I see that while most guitars have 6 strings, some have 7 or 8 strings. What’s that about? Can you get an 8 string guitar and play it as a 6?
If you are a hard Lefty, and you are not sure how this is going to go, I would (as a naive right hander) recommend a ukulele even more strongly. They are easier to convert to Lefty, or would likely not require that you pay a premium to get a Lefty version. Ukes are simpler in construction and require few changes to convert.
The few that I’ve seen / heard of have extra strings on the bass end, and seem to be mostly popular among metal players who want access to lower notes. In those cases, from what I’ve seen, the top six strings have the standard tuning.
That said, Wikipedia indicates that 7-string and 8-string guitars are also sometimes used by jazz and classical guitarists.
I’m a righty (though my left eye is my dominant eye), and when I first started playing guitar, I wondered why one picks with the right hand, and frets with the left. As a beginner (particularly playing rock guitar), it was the fretting that was far more challenging for me to learn than the picking / strumming.
My supposition (some instrument historian will likely prove me wrong 
) is that guitars have the lefty / righty setup that they do because, in the forms of music that were originally played on the guitar (and its predecessor instruments) relied more on complex fingerwork with the pick hand than they did on complex fretwork with the left hand. (Plus, I think that the default for Western stringed instruments seems to be fret left / play right.)
So a left playing a righty guitar in the righty way could be an advantage?
In terms of brand names, do some have better records than others among Yamaha, Washburn, Epiphone, Gretsch, Squier, Fender?
One’s picking / strumming hand is where the more complex work occurs. You want your dominant hand doing that unless you’re ambi enough to make a choice and can favor right handedness to improve access to guitars.
So, which is more demanding, fretting or picking/strumming?
Picking/strumming.
Think of it this way: If you can’t pick properly, it doesn’t matter how well you can fret (unless all you do is tapping, in which case you’ll be fretting with both hands anyway).
On another note: I’m also interested in why you want to pick up an instrument. What is your goal? If you wanna learn some tunes for fun, a uke or guitar sounds perfect. If you want to start making music, you don’t necessarily need to learn an instrument, depending on what music you want to make.
For example, if all you wanna do is make EDM, a good DAW and some software synths will serve you better than a ukulele. On the other hand, if you wanna make folk tunes you’d probably be better off with a guitar.
(I’m in the camp that can’t stand ukulele, btw. I can’t in good conscience recommend ukulele to anyone.)
I’ll offer the obligatory observation that perhaps you need to listen to more - or different - uke players. Sure, the Tiny Tim thing gets old quickly. And I’m pretty much a lightweight uke fan - and mainly bari. But I’ve been amazed at some of the diverse and virtuosic music made on ukes. I was on a bari uke forum for a while, and was astounded at the vids people posted.
And if you are interesting in keeping rhythm, the most important thing is the player, not whether he/she is hitting a uke/mando/etc.
Could you provide some Youtuber links of uke performances you like? To my mind, the ukulele brings up associations of Zooey Deschanel doing her cutely awkward schtick but I’m curious to hear whatever better part ukulele music has to offer.
I don’t doubt there’s a wide variety of uke music out there, I just really don’t like the sound. Even bass ukuleles. I can’t fault other people for liking it, though. I was just pointing out I can’t recommend it. I’m not a big fan of acoustic guitar either, to be honest.
I don’t think it has so much to do with the instruments as it has to do with what I associate them with, if that makes sense. I’ll concede it may not be completely rational.
I agree the player walks the walk no matter what they plunk on, and I’ll also offer the opinion that any instrument (even ukulele) can rise to the occasion if used well (or not, for that sake) in the right situation or composition. That still doesn’t make me like ukulele! 
Ukulele Hunt. The guy puts up videos of most of the songs. Look throughthe ‘tricky’ and ‘nightmare’ tabs section if you want to see some cool stuff. Here’s a good one.
Google The Ukulele Orchestra of Great Britain. They’re very entertaining.
And then there’s this -kind of the gold standard for virtuoso ukulele performances.
Any input on Fenders? Specifically Fender CC-60 or CD-60?
Decent guitars for the money; I have an older Fender as my campfire guitar and they tend to very serviceable instruments. Look at the Yamahas as well if you decide to go acoustic, and get thee to a local guitar shop that will do a decent setup for you, I can’t stress this enough. Try a few different body styles out to see what’s most comfortable. You might like a smaller guitar like a orchestral model versus a big dreadnaught.
A badly setup guitar will deter you from playing faster than having your hair set on fire. If you have friends that play, ask them for recommendations. If you elect to go lefty , your choices will be narrower overall for instruments, but it is generally easier to have your dominant hand strum/pick.
How do I know if the setup is decent or they’re any good at it?
I’m not going to disagree with you, or WordMan, on this, and I do grok it now.
My personal experience (and bear in mind that I am, as my college fencing coach described me, a “slow physical learner”) was that it was very challenging for me to learn the proper placement of my fingers on the frets to form chords, and to be able to move quickly enough from one chording to the next. Again, I play fairly simple rock guitar songs – 99% of what I wind up doing with my right hand is fairly straightfoward strumming, with little-to-no fancy pick work.
YMMV, of course. 
If you have any friends that play, ask around. Failing that look at store reviews. Thelink here gives you a how to setup but it will give you a good idea of what you’re looking for on pretty much any guitar. Look under Lutherie, Setup.
Bryan also has a good video here, Bluegrass Guitar Technique: Two schools of guitar setup - YouTube
BAsically, when you play the strings, it should be relatively easy to press down with no buzz. Don’t worry about doing the setup yourself, just treat these as a guide as to what to look for as the end result.
Don’t get too overwhelmed. http://www.guitarfriendly.net/acoustic-guitar-buying-guide/
Ditto. I can’t stand their sound. OK, “can’t stand” is exaggerating it, but “barely tolerate” is too positive a statement. Similarly, I love harmonicas. A not insignificant amount of people can’t stand their sound, either, no matter how virtuosic the instrumentalist is. Play an instrument you actually like the sound of–one that inspires you.
I’m not a great player, in any sense of the word great. Not even novice, to be honest. But I’d be way worse if I’d gone left-handed. It’s the same with bass – It seems as if all you do is thumping with your index and long, but what you really do is control the timing of every note you play. If I have difficulties with a part, I find it easier to slow down and focus on my right hand than to focus on my left. I might not always hit the right notes, but at least I’ll have the timing. Without the timing I just get buzz, which breaks the flow. A wrong note here and there is fine, just move along. Or, if playing live, as was recommended in the jamming thread, repeat it and make it work.
Harmonica is great. Pocket organ! And I agree, nothing makes you more inspired than something you think sounds great. And nothing makes you less inspired than something you think sounds shit.
Gotta reboot, sorry if this makes no sense.
I’ve bought lots of Yamahas and every one was always playable out of the box.
Now I have the APXT2- a parlor version of the acoustic electric APX. It’s great and super easy on the fingers to play. Not the best sound unpglugged, but is terrific plugged in. I personally don’t care for the big dreadnoughts, I feel like I’m trying to play a 55 gallon drum and my shoulders and joints don’t like it at all. But I am old and have short arms, so there is that.