I made a post a while back about how you can do objectives early, some were asking for video so… here’s if anyone needs a reference.
This is really only limited to destructible objects and special AI (dudes that drop stuff for the mission, they’ll spawn in specific locations on mission start).
Generally, if you know a mission well enough and recognize destructible objectives, destroy them before you’re required to and you can speed up the mission while the idiots on your team fumble around.