Just watching a guy jerk off in porn does nothing for me, but if I'm making him cum, that's a different story. I love knowing that I gave him so much pleasure and that he's enjoying it. The further he shoots and the more cum there is lets me know how excited I made him.
Every load is different. Some shoot down your throat. Some barely leak out. It also depends on how far in your mouth you have the dick. Most ends up on your tongue which is fine by me.
I've been with multiple guys many times but never saw the guys doing anything with each other. I usually have enough places to pleasure everyone involved.
I've fucked 4 guys at the same time several times before, but once in high school I was at a party and sucked off like 8-10 guys in a row in the bathroom.