Also: The product I’m talking about is called Soft Paws, www.softpaws.com
My two are littermates and I couldn’t be happier with how they interact with each other. They have never spent an entire day away from each other in their lives up to this point.
I don’t know how well it might work for adult cats, but I trained both of mine to just deal with it when I trim their claws. I got some special scissors from PetSmart and they work great. The cats usually get impatient so I have to work quickly, but they don’t fight it too much.
That’s our cats’ deal, too - two adult females who still hiss at each other regularly after 10 years.
We leave our cats alone for the weekend, too, and it doesn’t seem to have negatively affected them at all. An automated feeder so they can’t eat all the food at once would be even better (we leave Friday and come back Sunday afternoon, and the bowls are empty. If they ate it all Saturday and were hungry Sunday, well, that’s not the end of the world.)
My unsolicited advice for people getting new cats - train them from Day One to not sleep in your bedroom. Cats like to play in the middle of the night, and get fed when THEY want to get fed - cats used to not being in the bedroom will let you sleep better.
That’s been the received wisdom over the years, but it has been increasingly getting challenged for cats. The problem is, cats don’t really chew. They cut, puncture and tear, but they don’t masticate - as obligate carnivores their teeth and jaws aren’t designed for it. As a result there isn’t much removal of crud from jaw action. As far as I can find there are no controlled studies indicating cat teeth do better on average on a dry diet.
Meanwhile cats aren’t the best drinkers. Ancestrally most of their moisture content would have come from their prey. As a result under-hydration can occasionally be an issue, especially in male cats with their narrow little urethras. Blockages from crystal formation can be life-threatening and good hydration is the biggest key to preventing that problem. One article that goes into this in some detail.
All that said my cat previous to my current two lived to 17 on a overwhelmingly dry, free-fed diet without noticeable complications ( except occasional tooth decay issues 
). Like I said earlier many cats will do just fine. But there is some difference of opinion on the best approach to cat nutrition.
As for drinking water, they always say to have plenty of fresh water available for cats, but they don’t mention that cats like to find their water - my husband’s cat loves nothing better than a glass of water left unattended or the water out of a floral arrangement. I’ve started leaving a glass of water just for her to drink out of, and she’s always slurping away at that. Both of our cats love drinking out of the taps, too - just a small trickle, and you have to keep an eye on it so the water doesn’t run forever. This is all on top of the water dish that we have out for them.
My sister has a fountain for her cat, and it’s increased her water consumption by a large amount. She used to be prone to kidney issues, but not since she got the fountain.
I like the electric feeder because they can’t eat everything in sight, but I think I’d worry that there might be a power outage or something. For two days, it wouldn’t be a big deal if they missed a meal, but for long trips, I’d fill up my gravity feeders (I have two feeders for my four cats).
StG
Just wanted to say, kudos for wanting to adopt adult cats!
Two days a week shouldn’t be a problem, especially if it’s a pair rather than a single cat. I’d leave the radio on for them, regardless. :3
Haha! Or the TV, just to be sure… 
Yeah, I’m planning on not sparing any expense for the little guys/girls. Automation is welcomed, but not too much. Like someone mentioned above, I just don’t want to have to worry about something mechanical breaking down (unlikely, but you never know).
Gravity feeders seem to be the way to go, except that they might end up a little chubby. We’ll have to keep tabs on that!
I bought a fountain but the motor was surprisingly noisy so I never use it. You might want to check the return policy before buying one of these.
A high quality dry food should help keep this in check. The more real meat and less filler there is in the food the less likely the cats will be to over eat, at least that is what I am told. I have no proof, just the word of a couple dozen cat people.
Having two cats is so much more rewarding than having one. I think you’re making the right decision.
Maybe not littermates, but you can probably find cats that have already been living together for some time. There seem to be a lot available from people who are losing their house and moving into a building that does not allow pets, so they are trying to find a home for a pair of cats. Those are probably adjusted to each other already, just as if they were littermates.
And they are also harder to place, so you will be helping them even more.
Yeah, I was thinking that as well. I’m going with her to the shelter in a few weeks so we’ll check it out 