You might be ok. It tends to be the coastal resorts that get swamped in August - people flee the cities because they’re too hot. So whilst there will always be tourists, many of the locals/local tourists will be on a beach somewhere else.
We stayed a block out of El Ravel, which is a section of the the old city but a little less nice than the gothic quarter, felt much more of mix of local residents and stores to serve them, but still a mixture of touristy establishments.
It was walking distance to La Rambla, some museums, the Gothic quarter. Also walking distance to the subway.
The Casa Eliot Hotel was a converted apartment building, clean comfortable and nice decor, but nothing special.
I think you’re the first person in this thread who didn’t stay somewhere in Eixample 
From what I’ve read so far, I’m thinking El Ravel might be a little more gritty than what we’re looking for.
It’s really quite spectacular from the inside, it’s worth it to fight the crowds and go in.
I am back from this trip and just wanted to say: WOW, you were right about this! (inside of Sagrada Familia).
My four-day trip turned into a three-day trip when my overnight flight got cancelled, which was a total bummer. Nevertheless, the three days I had were excellent, and I’d like to thank everyone who offered advice in this thread.
We ended up staying in Eixample near the Diagonal metro stop, which turned out to be a good stop for the places we were mostly going. I did make it out to Montserrat, which was definitely worth the train ride.
Three days was definitely not enough time to enjoy everything the city has to offer. I plan to go back to see more at some point. It’s such a great city: beautiful architecture, easy to get around with robust public transport, delicious food, and friendly people. We did not run into any anti-tourist protests or anything, thankfully.
Did anyone reprimand you for saying Bar-SEH-lo-na instead of Bar-THEH-lo-na?
Nope, though that may be because I have a slight lisp
I did hang out a bit at the bar in my hotel and the bartender definitely pronounced it the latter way.
AIUI, the “th” for “c” is Spanish (Castilian), but in Catalan is “s” as in English and French.