did a little bit of testing on a 98se p2 233+gf2mx setup, 128mb pc66, maxtor UDMA-2 drive, sb16. not really surprisingly from the opening sequence it's clear that framerate is highly variable, it might be in the 20s and then at the default max of 72 in the span of a second, depending on view position. it never drops into the single digits unlike on a pentium mmx though so even though it's not great i'd say the game is kind of playable on this type of setup.
now the interesting part was, i immediately noticed a jarring constant stutter when moving the mouse, as if the game was skipping frames or something. i tried to pinpoint this by just trying to move left and right without the mouse, and even in low framerate scenes, it was indeed much better than when moving the mouse... then it occurred to me that i was using a (optical) ps/2 mouse, which i usually didn't do before with this game. i swapped it for a usb mouse and it was really a night and day change, looking around was a ton smoother now and any remaining stutter could be clearly traced to framerate drops. now it's no surprise that usb mice have a much higher polling rate but for the difference to be this jarring, i have never seen this to be honest. my setup includes disabling all mouse acceleration via windows registry. OP, what kind of mouse are you using? i'll also mention that mouse filtering did reduce the stutter a little bit, but i don't like that option as it seems to introduce a bit of input lag.
as for the other kinds of stutters mentioned, i definitely did get a couple of minor hitches when running around the scientists and one time a little audio hitch on the tram announcement, but i'd probably just put this down as a CPU or even HDD bottleneck. these are certainly much less of a thing on fast p3s. IME a lot of games from that time are really bad about actually leveraging large amounts of RAM to precache all their assets so i don't put much hope in going with higher than period correct RAM sizes, not to mention that 128mb was really top-end for 1998 anyway.
for an "ideal" video capture naturally a 60fps cap would be the way to go. even on a setup where you get a constant 72fps the game will look more stuttery than necessary because the 72 fps from the game doesn't evenly divide into the 60fps video.