Suppressing the UI
The reason I immediately made Sizer presets for the extra window size needed for filming in 2.0 to allow precise cropping due to the unmoving top bar is that somehow it felt like there's a reason that a totally suppressed UI isn't possible. The whole things feels very different in terms of hierarchy and relationship of parts.

If we actually get a suppressing UI I'll be overjoyed; if not, I won't be surprised. It's a waste to have to film extra - has anyone else found another solution?

Update: I forgot to say that when I first used 2.0 - the first minute I used it - I IMMEDIATELY looked to see if the particle issue had been fixed, which it seemed might've been as the UI is so different. Alas, no, it is still broken, as it has been broken now for years and may remain broken forever.