Yeah, I would just pick 1 format and use that - either 16mm or HD.
500ASA film can see into pretty dark places, and there’s even 800ASA and you can push BOTH to even higher ratings if you’re actually worried about using film at night. You actually don’t need much light.
The bonus of shooting HD is the instant gratification effect - you don’t have to wait for development and transfer (or PAY for it, for that matter). You can shoot it, and when you go home at night (assuming your editing tools are at home - but you get the idea) capture it onto your computer. The downside of HD is it is very high contrast - colors get too saturated too quickly, you can blow out to white (in which case all the highlight info is gone) and you can crush to black or grainy mud very fast without enough light (and all infor in your shadows lost) so you have to watch your lighting and exposure a bit more.
If you’re shooting HD, have a good video monitor with you, and if at ALL possible a waveform monitor so you can definitely SEE if you’ve gone too bright or too dark.
Good luck and happy shooting - hope this helps-
-Lew 