You do not want to go with a RasPi as the specs are no longer suitable for a Bitcoin Stack. There is a list of known good hardware here [Known-Good Hardware Master List] Hardware Capable of Running StartOS - #148 by erzdorf
Recommended OS Requirements
If you intend to run Bitcoin or store any meaningful amount of data, we recommend the following:
- Quad-Core CPU 2.5Ghz+ (boost)
- 8GB+ RAM
- 1TB+ Storage
For the windows machine, yes you will flash StartOS to a thumb drive boot from it and erase the hard drive. Here are some guides to help: