I’ve had 5 truck campers over the years. 8ft no cab over, Kodiak, Snowbird with slide, Alaskan, Cirrus.
Try without A/C because in BC there are lots of trees in the way of the scenery but the positive is you can get in the shade.
Order A/c pre wire from the factory in case you want to install a roof one in the future.
You will want an efficient 2way fan mounted somewhere.
Use the camper with the truck before you spend $1 on “upgrades”. Today’s trucks are pretty capable. Use the $$ and time for travellin’ and truck campin in places and elevations where it cools off at night...
PS - if you like to camp in the trees I would be tempted to get a quote on a pair of “branch rails” like expedition trucks have along the edge of the roof to help keep tree branches off the body work of the camper.