Flow, who knows how long it'll be until you get to AA if you get hired today but its definitely longer than most people should be getting hired at the major the traditional way. If you want to get to AA specifically, the majority of civilian new hires right now come from one of the wholly-owneds. (This isn't even really an Envoy perk, see PSA/Piedmont)

Upgrade, we're literally forcing FOs to the captain seat when they reach FAA minimum times for upgrade. That sounds like a fast upgrade but also keep in mind reserve times vary and many mid-seniority FOs complain about "no man's land" where you're too senior to get called out to fly, but too junior to hold a line. This sounds nice if you're trying to not work, but keep in mind reserve take home pay is about 1900-2300 per month.

I've heard from other regional pilots that our travel benefits are slightly better than the usual regional airline?

Outside of that I really don't know why you would look at Envoy at the moment. Every base we fly out of has other carriers with more competitive pay and better QoL contracts.