Well, if you are a seasoned fiver owner you are already aware of how things work in rv life. Don't pay too much attention to brands at this time.
Think floorplans, GVWR's and wheelbase lengths.
You will need go look at units and sit in them with all 5 people for periods of time to really get that camping and traveling in it feel to decide on a floorplan, then take from their.
As you already are aware, getting into a 5 year old rv is going to depend on how it was maintained by the previous owner. You should already know what to look for in that respect so there is no need to get into those basics.
Five people plus personal and camping gear is a lot of weight on a chassis. Watch your payload and make sure the seatbelt positions will offer comfort for long term driving.
** Keep in mind that hauling all that weight will be different than towing it. Adding weight to the rear compartments might lift weight off the front axle and make it drive like 'hell on wheels' .
Its not like your pervious 2000-2500# hitch weight over the rear axle, this new rv experience will put much of it behind the rear axle inside large rear storage compartments as well as rear kitchens and bathrooms.
Watch the rear overhang length, there is a formula regarding wheelbase and overhang length. You can
Google it.
You'll need to decide on your towing options for your model Subaru.
You might or might not be able to flat tow it, you might have to use a dolly or an actual car hauler trailer. You can search to see what others say about towing a dingy behind an rv.
Once you get all the class c basics in place, then you decide on a brand that matches you floorplan needs.