Am I the only one here who "try" to match the texture sizes with the faces sizes ? In other words, if there is a 2048 units cube, I would use 512x512 textures scaled at 1.0 (or 0.5) and if there is a cube at 64 units, use a 64x64 texture scaled at 1.0 (or 0.5).
It doesn't matter how powerful your computer is, because the engine is old and can be unperformant easly if misused.
+1
The good thing is that you don't need more than 100 fps to play any Goldsrc based game, as more fps would just create a mess with the entities (especially NPCs) making them turn really slow depending on how many frames you're getting (the more the slower).
I see a lot this problem with Barney (when you move him because he's blocking you), and I think this is a mistake made on Valve's end because if I remember correctly, the formula is "Speed = Yaw speed depending on the monster and the activity * time between 2 frames * 10". I think this can be fixed by removing the "time between 2 frames" variable but I'm not willing to try.
Also bunnyhopping would be harder for the same reason, being unable to maintain speed.
This would be very noticeable if you play on WON or you remove the bunnyhop cap limit on Steam. Otherwise, I don't think it's really an issue.