Did Tobey Maguire and Robert Downey, Jr. wear full costume when they could or only when mask or helmet was off?
I believe they tried to get them in the suit as much as possible. I mean, they paid for them and all.
However, a lot is CGI and, what you may have forgotten, stunt men.
For Spider-Man, I’m pretty sure that it was a mix. Some stunts were done with real actors (I assume not Maguire, though he might’ve done some himself) and some were done with CGI.
I think it was the same for Iron Man (combination of suit and CGI) though I believe they also used a lot of motion capture as well (CGIing the suit on later).
I’ve yet to see Iron Man, but, in all the Spidey movies, they always contrive a way for something to happen to the mask so you can see the actor’s face.
Plus, CGI Spidey is really, really obvious in the first movie. You can use it as a guide for the other movies. Anywhere where they would switch to CGI in that movie is where they switch to CGI in the other movies.
Robert Downey Jr really hates wearing the full Iron Man suit, so they created partial suits for him, and the rest, if seen on camera, was digital. I think on rare occasions the suit was 100% real, but I am guessing those occurrences were considerably lessened for the sequel.
For Spider-Man, it is usually a stuntman in any scene where Spidey is masked and doing any physical exertion. I may be wrong, Tobey possibly did a few of the simpler running and jumping shots himself. But the majority of the time, in the street swinging and fight scenes, it’s a digital 3D Spidey.
A 100% real Iron Man suit? Hollywood technology is better than I thought. 
Fair point. I meant every piece was physically assembled around his body. I don’t think anything was automated or could fly. Unfortunately.