Had a concern about going back to Win 7 - I've been reading on the MS forums and there is some concern that Win 7 keys are "consumed" by 10 and you won't be able use them again. After some reading it seems that if you have a good win 7 key and disc you should be ok to do a fresh install of 7 and be able to activate it. You might have to use the phone service to activate the key.
This could come in handy of you have a hard drive crash or MB failure.
I sure wish MS could have made this process a little simpler.
I am not as computer savvy as you seem to be. Wish I could answer your questions.
Right now, I would love to turn that One Drive off. Why do I need it???