I live at Capitol View on 14th St, and the floors and walls are thicc. As you said, nothing is 100% soundproof, but both my partner and I work from home and we've been grateful for how peaceful it can be here.

I'd look at units towards the south end of the building, where you'll have fewer neighbors and foot traffic. The building also has plenty of community space and amenities, is above a grocery store, and is a block from the park. If you visit, let me know, and we can show you around the building, plus our studio if you would like, and answer any questions.

The unit I'm about to link will have a view you'll shit yourself over. I'm not joking; one of the best in the city. We're two floors down and south facing too, and it's one of the reasons we've stayed here for going on 7 years now. The unit I'm linking is a studio, I find they have more usable space than some of the one bedrooms. Plus I think it will have a Juliet balcony so you can open it up fully and get plenty of fresh air which is such a plus when it's nice out or you burn dinner.

https://www.udr.com/washington-dc-apartments/u-street-corridor/capitol-view-on-14th/apartments-pricing/interactive/#/?floor-number=8

P.S. Love your username