BSO=Bicycle Shaped Object it is used to describe items of low quality that look similar to bikes typically sold at WallyMart KMart Amazon...they are designed to be throwaway items built from the cheapest materials and parts by the lowest skilled labor or maybe people who know what they are doing and just don't care.

In terms of wheel size, it is a wheel size. It doesn't correlate to frame size. Though typically a 24" wheel is usually found on kids bikes and that is where typically the frame size is nil and it is just by wheel size. However there have been bicycles for adults made with smaller wheel sizes either for shorter people or those afflicted with dwarfism or other skeletal-muscular issues or in some cases just for compactness or other reasons (Tern GSD/HSD uses a 20" wheel to make a smaller cargo bike for the city for easier storage but ability to haul 2 kids and also keep the load lower to the ground)

I would go down to your local bike shop and have them size you up for a bike. If you are differently proportioned I might reach out to your local bike fitter and set up an appointment and use that data to go to someone like Lennard Zinn/Zinn Cycles or another frame builder and have them build you up something to fit you well. Your fitter might even know some local folks or have ideas.