Just wondering what glitches/tricks used in the speedruns could still be performed in the latest version of this game.

There's a rather big list of things you can do in co-op and a smaller list for solo. As far as I know it's not written anywhere, so I can't really give you that accurate of an answer. A lot of the maps are changed in the latest version, patching out several shortcuts and such, with Dead Center probably being the campaign with the least changes. For tricks you cannot infinite stumble (the thing people do in solo at the start of Swamp Fever level 1). What you can do is cornerwarping, grenade boosting, grenade launcher boosting; so pretty much everything that would be used in co-op. The most noticeable changes are indeed in the maps but not really the mechanics of the game.

there are a lot of specific skips that where patched in some way. the only mechanic patched was infinite stumbling, but everything else works. it's more on maps specifically being patched. Examples are: Passing 2, skipping the underground event, Passing 3, skipping the elevator, No Mercy 3, breaking the door with melee weapons and GL shots, Death Toll 3, for co-op, triggering the end saferoom from the front of the saferoom door, Dead Air 3, common jumping at the beggining of the level.

There are many other patches that happened, but these are just so you can have an idea that many skips in particular were patched.

There are also some skips that they attempted to patch and did it poorly so there are still workarounds. Examples of that is the Dead Center 1 window skip near the beginning that just requires a different technique, and Dark Carnival 3 coaster skip which requires a couple of different jumps to do the same thing. A Parish 2 fence at the crescendo was blocked so you can't go over it in solo, but you can still abuse warping to get through it in co-op.