Powerlifter, I am not going to pretend that I know half as much as most of the others on this forum. However just over a year ago I was in the exact same place you were. Bikes have change a ton since I was a kid and built them out of the scrape pile in the back yard. The only real difference is that I was pushing 350lbs when I started.
Like most have said If you are going to use your REI gift certificates all the bike that you are looking are are close in quality. After reading through your thread you should be alright with pretty much any of the bikes you have looked at. Just make sure that it fit your frame. Then start saving your money for a nicer better quality bike later down the road, If you decide that cycling is not for you then you are not out a ton of money.
When I started I purchased a hardtail mountain bike and rode it 95% of the time on the street, yes it requires more energy to ride it on the streets then a hybrid or road bike but the extra resistance provided by the mountain bike helped me get into better shape and lose some weight.
My first ride was only about 2.5 miles and I though I was going to die, but I continued with it and rode over 6000 miles in 2016.