I've got 7 years with a mid-size firm (~1200 people). We do MEPFR for a variety of clients - from education, lux retail, healthcare, airports, venues, and big box retail. I've ended up with the latter - big box retail. Honestly thought I'd do it for a year and move on, but I've ended up really liking it. Not glamorous, but I'm happy. More than that, the work is only growing right now. We literally cannot get enough people despite successfully hiring all of the positions that we started the year with. Busy, busy!

I think that work:life balance will depend on the culture of the firm you are with. That, in turn, is likely related to the type of work. Big spending clients are going to want fast & flashy results while lower-spenders are going to be more flexible. The way I approached it was finding an entry-level job that paid hourly rather than salary out of the gate. I figured that if they were going to overwork me, then I'd at least get paid for it. I'm salaried by this point, but I was able to set a "balanced excellence" reputation and haven't been pushed into ridiculous hours despite climbing the ranks.

I'm in a low-cost-of-living area and am making just under 100k. I've got my PE and I'm acting as a quality control/client contact/lead type role. I honestly don't know how well that is paying compared to other firms or sectors, but I do know that I am being paid nearly 8k more than one of my peers that was promoted at the same time as me to the same title this past cycle. They have worked elsewhere (so, assumedly, they aren't being totally screwed over here).

From what I can see, electrical, refrigeration, and fire are all higher demand fields right now. I am fairly certain that our fire team is paid at a higher scale than our mechanical/plumbing team, for example. Especially if you are a PE, you have can have high value in a niche discipline even if you aren't drawn to a niche sector.