I tend to play it by ear joining teams. I prefer most content at +0 and "at a good clip" I do not say speed. I have seen true speed runners. I absolutely can not keep up. Or if I can I am arriving as the fight as over. Keeping pace with the team and providing NO assistance. Yet I do know the content and move at a good clip. I have heard some people complain I go too fast. Perception is everything, but I know what "true" speedruns are. I cannot do them.
I like ITF at +4, but I still want the team moving along. If a team cannot get through a +4 ITF kill most at a decent slip there are issues. In my opinion. I have been on many an SG team that have done the ITF (+0) at under 15 minutes, and the speedrunners in that group had posted and verified times in the single digits. I think 6-8 min? Not my record, do not remember.
When I lead TF/SF teams I almost always run at +0 and advertise as "quick runs", or "as fast as we can" or maybe "speedy-ish" again, I do not consider what I do speed running. just, fast... Get in, hit the mission requirements, move on. Sightseeing is for people who have not played the game a long time. Solo it if you want to read, or make your own team.
When joining other teams, unless a kill most/kill all, I will try to move things along. Stay "near" the team, but try to get the goals done. Team awareness is important. A good example is the Tarikoss. Some of those missions just need 1-2 peeps. Some you split up to find objectives. One, with Longbow, you need to have good team awareness, and good objective awareness. You only split one or two stalkerish peeps off as scouts. Stay together....it is faster. I like fast.