FedEx is a great job. My buds at SWA tell me that's a great job too. When I was only a few years out of SUPT United was the great job...times change... See where your timing puts you!
C-17 vs T-6: I would follow the USAF path that works for you. Either should be fine for future job interviews. USAF pilots are a pretty well known quantity and neither airframe should put you at a disadvantage in the civilian market. Maybe the C-17 time would be a bit "better", but don't ruin a marriage or anything over it.
Right now new guys are S/O's on the 727. We're supposedly retiring the 727, so that may change. Whatever, it's a job. S/O isn't a bad place to start. I've been doing it 4+ years, some guys will probably only do it for 8 months. Again, whatever...
Frequent flyer miles are yours to keep. We generally fly Delta, but I'm not an international guy so they could tell you more (since they earn a lot more miles). You can use them for whatever Delta miles are good for.
A majority of FedEx guys commute. Any major city is doable. If you join the Guard or Reserve, either live near your Guard base or at your airline domicile. Don't live in a third place and "double commute".
FedEx can't force anyone to live in China / Hong Kong. Our foreign domiciles are volunteer only.
As for the "I've read comments about people flying 350 hours but being paid for almost 1000 in a year." question:
It's complicated. In a nutshell, we at FedEx don't really get paid per flight hour. There is a hugely complicated matrix that determines what a trip is "worth". A one day trip will always pay at least 6 hours, even if it involves a 45 minute flight to Nashville and back. A two day trip won't necessarily pay 12 hours. Whatever. It's a job. You'll learn more when it matters. It's a good job, so don't stress too much about the details.
You'll learn a ton on this forum. Soak it all in and don't get discouraged. Keep asking questions and keep a thick skin.
FedEx is a great place to work. Just remember: It's a job.
(All of this is one new guy's opinion. It's also oversimplified. It might not even make sense. I might not even be a pilot. Happy Internet.)