Know that once you become an AO, you have left the life on an engineer. Its a sweaty job with a 6 month to 1 yr training program. The OT does not factor in until you are fully qualified and we are talking (your positional quals, fire brigade, safe shutdown, first aide, etc). This is of course based only on my experience to date. Fully qualled guys are going to get OT before partially qualified guys. Its only fair. Basically don't count on more than your base hourly, especially the first year.
I don't think AO will prep you for engineer if you decide to switch. Sure having practical knowledge and walk-down experience of systems is a plus, but nothing is stopping you as a young engineer from going into the plant to walk down systems and following operators around.
You can get to the control room from the engineering ranks as an Instant or STA.
Just make sure you get the big perspective before putting your NE degree on the shelf. You're not going to be using it at all if you go AO.
We had 1 NEng in my NLO class. He struggled through training and eventually took an Rx Eng job in NY. Just saying I think it was a culture shock for him. He was wired for design, theory, and rx testing, not memorizing specs and settings...and cleaning up oil.
Good luck with your choices.