Hello! I have a few questions about things before I want to start speedrunning. First, is it ABSOLUETLY required to use Bunnymod XT? Second, do I need to worry about whether or not I use HD models? Finally, can I use a completely steam version (steam dlls and steam client) to do my runs?

Hey! You absolutely need to use BXT for your runs to be verified. Secondly, it's your choice completely if you use HD models or not. Thirdly, you can use the latest Steam version of course, but note that those runs will go into the Steam category leaderboards.