1. is there somewhere on the UI where I can see the light level outside of stealth?
I think left shift is the default key to show sight cones and light levels outside stealth. The keybind can be checked or updated in settings.
2. I might be confused but at times during combat you can switch between characters - like all your members share one turn, but at other times it works in a different way. What is causing this, does it have to do with rolling the same initiative?
That’s almost it, though they don’t need to roll exactly the same initiative. If your characters are next to one another in the queue, they can take their turns in whatever order they like, but they can’t if there’s an NPC between them in the combat order.