UV master flattened map vs uv map tools on right tools column


If I use the UV Master plugin to unwrap uv’s, and can view it in flattened form, isn’t that the UV map? Most tuts I’ve seen just stop there as if the UV mapping is complete.

A bit confused (even after watching tuts) as to how this correlates with the UV Map options in the right hand tools column which has specific types (spherical, etc) along with Map size controls which are missing in UV master.

I’m thinking I’ve missed something here. Does UV master NOT create the finished UV map, but rather just provide info necessary to generate a mav via the other set of tools?

Online docs seem to indicate they’re just two different ways of creating UV map… but if that’s the case, how can I unwrap while determining seams like UV master, but then also determine custom size like other toolset?