... as a UK candidate aiming to study in the US, should I take both ACT, and SAT?
If I do SAT, I'd do subjects: Physics, Chemistry, and Math 2, essays aswell.

I've already done my A-levels, by the way, and left sixth form. I just don't want to go to any of the UKs shitty universities, with their restrictive no major, combined honours, bullshit.