Around a year ago I made a TAS for this game, which you can see here:

The biggest discovery that I found was the deathwarp. By avoiding checkpoints, you can open the chest and then die to return to the hub immediately. This is only possible in 3 of the levels, and one of them is probably TAS-only (it might be doable with a ton of practice though). The top left deathwarp is pretty easy and I did it in my PB of 4:54.

I also managed to find a glitch which as far as I know is completely useless, but it is interesting nonetheless.

Yo that's sick, I've been practicing the last couple of hours and can already tell I won't be doing all that.

Except for the top left one that is. Like you said that one's pretty much free to go for and definitely a timesave. Within half an hour of runs I almost beat my PB. But I did practice the bottom right one too and I did get it once but it's so inconsistent/I lose so much time just trying to be careful that for now it's not worth it yet, but very cool find and very cool TAS