There is no emulator that can currently do everything needed to make what I consider an acceptable TAS of the game. I currently use a modified version of BizHawk made by Cronikeys for my YouTube channel, but I've been delaying working on a full game TAS until emulation some day improves. Here are features that I think an emulator needs to have:
(1) TAS tools - Duh. Bizhawk has this.
(2) Proper saving - The version of Bizhawk I have has this and maybe some of the newer main versions do too. Not all emulators do though, but this is absolutely essential to basically any route in this game.
(3) Fixed graphical spiking - This doesn't have to be 100% fixed, but with the version of Bizhawk I use it can get really bad in certain areas (
https://www.youtube.com/watch?v=jLdZZn19uVw for example ). This isn't an absolutely essential fix, but it is extremely distracting sometimes, especially with Tiny. It invites the viewer to question the validity of the run and distracts the knowledgeable viewer from what is going on. If graphical spiking was just one or two frames every 30 seconds that would be acceptable, but in a lot of areas there are more spiked frames than unspiked frames. Apparently some emulators are better than Bizhawk in this regard, but I have't verified this myself.
(4) Fixed random tree warping / telegrab - There is a glitch in the game where after a technique called tag barrel storage, if you grab a tree or climb a ledge you can teleport to another location. However, on emulator, sometimes this will happen randomly with no prompting. The version of Bizhawk I use seems much better about this than, say, project64, (especially with regard to random grab boosts) but there are still several places where I need to go out of my way to avoid mysterious teleports while climbing trees. It turns out this isn't important for any%, but it would be a nice fix for, say, a low optimization tool assisted demonstration (LOTAD) of 101%. This is supposedly related to graphical spiking.
(5) Accurate lag emulation - Lag is SUPER IMPORTANT in DK64 and serves as the basis for how many tricks work. The emulator I use is pretty good, but not perfect about this. It is certainly good enough to do a TAS, although any improvements here would be welcome. A fun test of this is to watch the intro demo - if it desynchs and DK falls into the water, it is probably because lag isn't emulated correctly.
(6) Proper photos - When the camera is used to capture a fairy, a photo will appear on screen for a few seconds to show what you just took a picture of. Some emulators this doesn't work on; the one I use it does. However, the photo stays on screen for too long before transitioning to the fairy cutscene. It looks weird, and it costs a few seconds each picture, and it would be really great to fix this. It isn't a dealbreaker though if this can't be fixed.
(7) Better loading time emulation - Some areas like DK Isles or Frantic Factory take noticably longer to load on emulator than console, and may exhibit what I call a "double-clutch" load (you'll know what I'm talking about if you watch the load). For most games this can be dismissed as a "whatever" minor time loss, but this actually breaks the route for any% due to a universal timer trick called Intro Story Glitch. I really, really, really want better loading times (it doesn't have to be perfect, but something similar to console please or even a bit faster if need be) before starting on any any% run.
