Re: How many engines
I have long maintained an Air-cooled piston port two stroke is one of the most reliable engines in the world. Only three moving parts if you don't count the reduction gears.
Crank, rod, piston.
The rest is details...treat these engines like they were designed and they last forever. Most quality related failures will occur within the first few days so once it's sorted out, they just do miles. I recently sold a running ht with well over 10k miles of 250lb adult use.
Still running the new owner back and forth from work every day.
If more is better, then too much is just enough.
If you can't afford it, build it yourself.