Re: Many questions, wanna make a purchase!
It all boils down to your skill building and maintaining the bike. I ride a cheap POS Next that most people would say cannot take what I do to it every day. It stays running because I identify and fix any potential problems long before anything fails. You sound like you have some bike experience so you should be okay with a cheaper bike to start with. I also think you are DEAD WRONG thinking motorized bikes are the same as human powered bikes as far as the stresses the bike sees. You may not have ever seen a hub seize solid and self destruct because you have never ridden ANY bike at the sustained speeds and loads the motor can impart. Just tooling around at cruising speed will put more stress on the bike than a human riding at 99% would. Don't underestimate the potential for serious failure and injury if you don't know what you are doing.
If you treat the bike right, there is no reason you cannot get years of fun and reliable service from a wallyworld special. Just don't think it will be easy because you already ride a bike. A motorized bike is a whole different world as you will discover.
Buy the bike you like and TAKE GOOD CARE OF IT and you will be fine. Study the numerous threads on budget builds, there is a LOT you need to learn to stay happy and safe as you explore the thrill of riding your newly built motorbike!
If more is better, then too much is just enough.
If you can't afford it, build it yourself.