GT is a good beginner, but look st Giant bikes. They make a lot of other brands, nut their own brand offers a greater value. (No middle man)
29 is the way to go and your height doesn’t affect it the engineering and geometry. My write is 5’0” and loves her cannondale 29er.
Yippy can find great used bikes for a better price. Like motorcycles, people buy them with the best intentions but 50% never ride more than 50 miles and the bike will be in great shape. Craigslist, KSL, or many larger bike stores will take great trade ins.