While what input method you use does affect how easy certain tricks are by a lot, I've never seen a leaderboard split up by what you used to play it. For example, on shmups forums, it doesn't matter if you used a pad, stick or keyboard to achieve your score, it's treated the same (although turbo on/off is a category for games where it matters, like Darius Gaiden). It's interesting to note of course, but ultimately you should learn the input method that's fastest for the game if you're seriously into it.
You can never become 100% legitimate unless someone watched you play it live.
For example, you can take a TAS of an NES game and use a NESBot to play it back on real hardware and use a capture card to record that.
Remember, legitimacy, or likelihood a run is legit, is not a binary yes/no, it's a continuum.
Think about how ridiculously hard it is to make an N64 emulator.
Now imagine the same difficulty, except it's a different, rare console with even less documentation and almost no games or interest.
Why would anyone want to make an iQue emulator? It's extremely esoteric.
If you want to quickly test if holding down a lot of keys at once will work or not, open up notepad, (make a bunch of text if it's to do with arrow keys so you can see the result) then hold them all down and see if the last one registers immediately, or only if you let go of some keys.
It's not going to get rejected now, no.
But if you made an 'even more 100%' TAS than the current 100% TAS, and it was just as high quality, it could obsolete this TAS.
The user of bizhawk may quite reasonably expect bizhawk to behave consistently among cores. The user of any software may quite reasonably expect to be in control of when changes are flushed to disk. Savestates dont appear without the user putting them there. Why should savefiles? Because the user indicated it to the game, OK I get it. That will work, right up to the point where it doesn't.
We'll probably add an option for all the cores at some point in the future, but I'm not sure what the default should be. I'd rather work harder on training the user to be in charge of things, instead of depending on mushly emulation metaphors and automagic.
The intuition of saving in a console is that you can turn the console off and on and the save file is still there.
For the emulator it's the same idea - you should be able to turn the emulator off and on and still have the save file be there. Except now there's a 'meta turn off and on', where you close and re-open the emulator entirely. Technically it's a different operation, but it intuitively feels the same as turning a console off and on.
Savestates are different because they don't exist on a console.
You need to record your normal playthrough and present to the audience as an input file when submitting your TAS.
In particular, it doesn't need to be a TAS, or even very fast, but it needs to be an input file that, when played back, results in the save data that you use for your TAS.