Just my opinion here:
Forgo Ares, way to many negative feedback from people.
Get the PSA upper, it will match up the best and offer you the tightest fit and finish to the lower.
I like your lower choice but.... If you go collapsible, maybe get the CTR with the LaRue riser for better cheek placement with optics. BUT: something with PSA response bothers me, why can't you use a rifle extension? Because they don't?! It sounds like they are idiots, went the Voltr rout and never looked back. I think you'll be fine with rifle length.
I like your barrel choices and 20" will be fine, as will 18 or even 16. Good rail choice too. If you buy a bolt from Rainier when you order a barrel they will headspace for you.
Welcome