I’d say the real answer depends on what conditions you’re shooting in. If you have a 400 or 600 2.8 they make a gigantic difference over a 200mm lens both in real reach, sharpness and importantly bokah. But if you’re shooting on a hot football field for instance you’re going to run into distortion from the atmosphere.
Honestly there is just very little comparison between a 200 and 400, let alone a normal focal length lens.
Are you going to mount lights behind it? If so how do you plan to move the frame? What kind of ceiling is it?
Lots more information needed to give an answer. Try searching for ceiling mount on B&H for some options. They make track systems for lights or you can just use any old hanger.
You can shoot the first three songs from the pit and then you're done photographing. Nothing from the crowd. They may let you stay and watch the show, but no more photos.
Three songs lets you do a surprising amount. You're almost certainly not going to get on stage to shoot the crowd so don't worry about that.
Move around. Pay attention to the lights and try to use them as good backgrounds. If they have a giant screen behind them watch for banding. You may need to drop your shutter speed down to 1/125 or so to get the screen image without banding, but you will run into motion blur so you'll need to figure out what you want.
I assume since you've been photographing concerts that you know you'll almost certainly want to shoot in manual mode and expose for the performer. Shooting raw can be helpful. If you have two bodies it's generally easier to not switch lenses. You won't need anything longer than a 200mm most of the time from the pit. If you're ever stuck at the sound board bring the longest glass you have and a short collapsable stool.
The most important thing is to relax and have fun. It's just a concert. There will be more in the future so don't get too worked up about it. Understand that you're going to be in a tight space with other photographers trying to work and security guards who have other things to focus on. Play nice with the others and don't just camp out in one spot.
This is the correct answer.
If you’re comparing the godox v1 to the godox V860iii, in my experience and from the reviews, the v1 is much more durable than the v860iii. Don’t know what’s the issue with the v860 but they have a nasty habit of dying in a year to year and a half.
I have both and the light is basically the same unless you’re shooting a specific shot against a wall. The V1 does have a really handy magnetic attachment mechanism that lets you put gels and a diffuser on it super easily which is actually the main advantage.