Pretty much all I do is use "modern" monitors. I don't have much in the way of monitors. I picked up very few monitors though. For some reason they usually weren't in the same waste stream as the computers themselves. They tend to not look good and have serious issues. Like my Sony whose case is cracking for some reason, or the other Sony whose gigantic gray plastic back is turning a shade of brown-gray. Even if I could get it off, non light colors tend to not respond well to hydrogen peroxide. I bought those, I only ever salvaged one monitor, for Macintoshes.
I've tried in the past to add USB to some systems, unsuccessfully.
I value originality more than I used to. I think twice before swapping CPUs and adding drives. That said, sometimes it's the right call. That 56K modem, well, I literally can't do anything with it. That 32MB of memory, well, here, have a few hundred more.
I should really be adding NICs to systems I go past without them, but the issue is I don't have a gigantic ethernet cable to go across the house from there to the router I guess. Maybe it's time, 🤣. I just don't spend much time doing this anymore.
On the P100 I picked up last year it had for whatever reason an unconscionably loud fan. It wasn't failing, it just made a hell of a lot of noise for the task. I added an in line resistor (not modified, it's a Zalman part) to give it a rest. Still works just fine, and about half as loud as when I got it. It's a P100 with a fan, it's not going to overheat.
Just to see if it worked, I dropped a P233 in and as you might imagine (I don't even think the board has jumpers for it, it was at 200 maybe) the system was far more responsive and generally nicer. Also it felt a lot less like its age. I already have plenty of P233s, and I didn't need it here, so after testing the chip I returned the P100 to its original home.
In retrospect, I did a lot of stupid things salvaging when I was younger.
I can foresee a time where you just don't have the parts like a hard drive or fan or whatever and go to more modern devices, but I happen to enjoy the hardware side of things, and you better believe if I had a phone line I would in fact be using the 56K modems to grab drivers and crap for systems I work with.