A couple years ago the Winn's and I believe the owner of AM solar we're doing reviews of flat panels and there were a couple key issues with them. One issue was dirt collection in the dimpled areas. Maybe they are selling different panels now, you could search the issue.
Figure out what gauge the wire is. It seems that manufacturers often use 10 gauge and if so you could run a larger panel. Check to see what controller you have. It takes the same number of holes in the roof to hold a 100 watt panel or a 180 watt so I'd lean toward as large as possible. You may not need that much but you have it if you dry camp etc. It's not much more money to go from 80 or 100 to 160 180 if roof area allows.
Panels will have mc4 connectors on them or a junction box on the back.