I have a soft spot for Appies, and that girl is pretty............and fed! Is there a hay shortage in your area, ALL of the other ones are underweight. 
The free chestnut looks too long to carry a larger rider well. You want to look for a short back, thus stronger. Also he looks to have upright pasterns and probably shoulder, can't tell from the pic. This would equal a choppy, rough stride. 
The Appy's pic isn't a straight side view, but she looks nice to me. Can't tell about her head/throatlatch, but her neck ties in high to her chest, her neck looks to be a good length, shoulder slopes nicely, looks short backed, NICE butt, nice long croup and though the pic doesn't show clearly I'm guessing her hind legs are well set. Only concern I'd have are her front legs. The off fore (right) knee looks wonky to me, and both legs are set back under her instead of straight down. I can't remember what the knee thing is called, but it looks to me her knees would be prone to buckling. I'm a big girl, too, and I don't want those legs giving out from under me!
Of all you've shown, she's the only one I'd look at. The dark gelding is long and skinny. Maybe his owners don't realize that green stuff is all weeds?
The palomino mare is pretty colored, but again is long backed. And, if that's as good as she looks weight wise, I'd way pass. I'd be embarrassed to have something that skinny in my pasture. Old does NOT equal skinny. Look on the archives on fuglyhorse blog, people have horses in their thirties who don't have spines sticking up like that. She also looks to have an upright shoulder and pastern, thus short choppy strides. Well broke, reasonable young horses are a dime a dozen these days. Take your time, and PLEASE have someone experienced go with you. SO many horse people would love to go shopping, and we all love to give advice, don't we 
Good luck on your search. Course, if you have a jersey heifer you're wanting to trade, I might start looking at MY girl with a new eye. I don't ride hardly at all anymore, and am coveting a milk cow