You may be aware that UE4's lights can be set as “Static”, “Stationary” or “Moveable”. When you place a light in a level, it's set to “Stationary” by default, which pre-computes lighting for static objects, but still illuminates dynamic objects (such as the avatars) and casts dynamic shadows.

Long ago, I got the impression from the documentation that static lights won't illuminate dynamic objects at all, which would obviously be not much use for ZGA levels, since the avatars need to be illuminated everywhere in the level.

I've just discovered that they actually will illuminate dynamic objects though, including the avatars, albeit with a few limitations.

The main benefit of these static lights is that there's virtually no performance cost to them at all, so you can use as many as you want to illuminate the level well, and you won't get that irritating warning when you've got multiple overlapping lights. Furthermore, you'll get better performance in general than with stationary lights.

The main downsides to static lights are that they don't cast shadows from moving objects, and also it seems not to produce as strong directional lighting on dynamic objects, if any, as stationary lights, which can give the characters a flatter look.

I've tried setting every light in Factory to static, and it's yielded quite a large increase in FPS. I'm not sure exactly how much, since it's maxed out at 144 now.
Honestly, it doesn't look much different to before so far as I can see. The shadows were nice, but you don't really notice their absence.

Anyway, if you're wanting to improve the performance in your levels, or illuminate them better with no performance loss, static lights may very well be something to look into.
Quite possibly a hybrid approach may be best, with static lights for the majority of the lighting and stationary lights in key places for effect.

I'll post an update when I've experimented some more with static lights, and possibly make a new lighting video.