For vehicles: if I choose to build a team with a piloted vehicle, said vehicle must have a pilot, otherwise it's just dead weight?

But, if I chose to build a team on autopilot, it can perform actions on it's own? If that's the case can it still be piloted?

I'll just leave Tabletop Teacher's video here.
https://www.youtube.com/watch?v=DsyGB2EDB5I

Better yet, I'll link to the Comprehensive Rules Supplement and Preview for Tony Stark's Car, both of which include the up to date Vehicle rules.

I am very appreciative of Tabletop Teacher's videos and I think they're a great tool to clean up play for people that know the rules or give a intro for people that don't. However, he has made mistakes before, as we all do. The problem is, his mistakes are taken as gospel and left up as videos forever.

So, for answering a rules question, the rules are the best source.

To the OP's questions, yes. A vehicle cannot be given actions without a pilot unless it has the Autopilot Trait (which all old Autopilot dials have by default). And all vehicles can be piloted (unless they have a trait or something that says they can't).

On the subject of Autopilot, all Vehicles prior to the Nick Fury, Agent of SHIELD set that had Autopilot dials were given errata to have the standardized Autopilot trait- That appeared on Vehicles in NFAoS and after. The older figures with Autopilot dials can now be played normally using either dial, the only difference being that the Autopilot dials get the trait.

With the 2017 rules, a separate Autopilot keyphrase ability was added- These are functionally different things. I don't believe we've seen anything so far with the keyphrase ability.