The 7'6 addvance has a lot of volume and paddle almost like a 9.0, it's very stable and has quite some performance built in it, it has enough rocker (actually more than the 6'10) to handle nice drops when it's hollow and still goes super well in the slow parts, so it is perfect as an alternative to longboards as it is much more manoeuvrable and super fun.
I weight 90kgs and i'm about 6 feet tall. I tried different fins setup but the one i like best and always use in all conditions is the MRTFX rainbow + the Firewire deviant fin. You can also put a standard trailer as the rear fin but i find the deviant will turn the same but has more drive.
The 7'1 Activator is much harder to paddle but is faster and turns much sharper. Coming from longboarding, you will have no problem to adapt and find your marks straightaway on the 7'6 addvance, and if you don't expect to make big airs, you will catch a lot of waves and have a lot of fun, That's for sure.