Good questions. None of them dumb
So far OpenPPG (Paul and Zach Whitehead, aka the White bro’s, etal) have offered the four motor X4 and the single motor SP140 models. So yeah…two. afaik the SP140 has not shipped yet. Six batches of the X4 have been shipped. There are running improvements to the model between batches.
The X4 sounds like a swarm of angry bees. Or exactly like a really big@$$ drone. It’s not exactly quiet but I fly mine without hearing protection. Check the videos for more. The SP140 is definitely quieter.
One big prop is always more efficient than 4 little ones. They don’t make as much noise so more battery power is being turned into thrust instead of noise. Also in electric I think (might be wrong) that one big motor can be more efficient than 4 little ones as well. The differences are small though.
The X4 is now offered as kit only. See the several build logs on these forums. The SP140 is available as a completed unit. It’s probably not feasible to try to adapt the motors/electronics onto something else. If you can swap Tesla motors, batteries, electronics, into a random BMW then you could probably build your own electric PPG.
I haven’t delved into the ‘open source’ parts myself but the CAD files for the X4 are apparently on GitHub. You can download and cut your own CF plates and mill your own aluminum parts and program your own chips and circuit boards, and print your own 3D printed bits. Probably wouldn’t be cheaper but you wouldn’t have to wait for OpenPPG to create and ship a batch. People in this community have contributed to the design improvements included between the batches and others have provided 3D part files for improved wiring and switches. Walk through a couple of the build logs to familiarize yourself.
Be patient with us all. You should see a few more posts for additional information here as soon as someone is not out flying.