I have WC1/2 and noticed that WC1 has a sound glitch problem. Did GOG ever fix this? Also, anyone else have wildly inconsistent framerate issues with WC2?

I don't know about the sound glitch but I think I might have done some tweaking to get it to sound right. I don't remember and I use an MT-32 emulator now anyway.

WC2 is like that. There is no speed throttling so you have to change speed mid mission with DOSBox controls or deal with slowdown. I've read that slowdown was a problem for the original DOS versions too. I can't confirm because I never owned it then.

Yeah, there's not much you can do about the framerate issues short of adjusting DOSbox's emulated CPU speed in-game. Fortunately, it's much less of a problem in WC2 than in WC1.

I've noticed that changing the CPU core from Auto to Normal helps out a lot with both the framerate issues and the joystick (which is way too sensitive under what I'm guessing is the Dynamic core).

Audio issues can be a lot of things, but if you're getting stuttering audio, that's a case where you've either got your CPU cyles set too high, or your blocksize under the sound settings too low. I haven't seen that problem on an actual PC in years, though. My android phone running the least optimized port, sure, but not on a real PC.