Hey there, hi there, ho here- Welcome!
Just my opinions after 1 build and one planned- former road cyclist and bike mechanic-
It doesn't sound like you're gonna be a "custom" guy, just the meat'n potatoes kind of transport- cool!
Most people like a 26" cruiser- really can't go wrong for the kind of riding you mentioned-
The newer ones are much lighter than before- both frame and alloy rims. I recommend a smooth tire, and a little more narrow- I put 26 X 1.75 s on mine- and a BIG difference in rolling and ESPECIALLY vibration- 2.25 knobbys are heavy, don't roll, and shake you with a motor. I got some for less than $10 a piece at a local bike shop. I've now even got a 27x 1 1/4 wheel on the front, and added a campy brake to the added suspension fork, and may even go 27 in the rear.
(but I've also got a Schwinn 10 speed in the wings to motor)
the newer cruisers need a bigger clamp for the down tube mount or other modification- I ground the mount down and put foam pipe insulation in- also save vibration! but I think the newer kits mostly have an adapter mount - a nice feature to save effort.
I have the standard 66 cc kit (usually called an 80 cc) and these are the most prolific- I may try a slant head 48cc on the Schwinn- mostly for weight and noise reduction- but for a better cruise I put a 36 tooth sprocket on the micargi cruiser (multi-speed- I like the hand brakes and have a double ever now that works great, and I want to be able to pedal as normally as possible. I don't think the motor kits are thatr different on these two cycles, and the 66 isn't overpowered, and runs best not wide open.
Here's pictures- the cruisers been changed now but I haven'tr built the Schwinn- for that I have a narrow sproket and smaller chain and ultra-light 34 tooth sprocket for the ground down strandard hub- with alloy wheels I'm expecting the finished weight to be not much more than 35 pounds.
Good luck- I think you'll do exceptionally, but this forum is still a great resource.