Bevels don't work well if mesh has lots of polys? Or am I doing this all wrong?

Hi all,
I’m trying to understand how to add bevels to objects with high polys. As an example, I made a sphere with level 3 subdivision modifier. Then I copied a 2nd smaller sphere to boolean from the 1st (with BoolTool).
I want to bevel the edge of that boolean. I thought that the problem is selecting it.
I did select hard edges, then tried to bevel that but it was terrible.
How am I supposed to do this? What am I missing?

Bevels don’t work well with n-gons, and if you boolean two spheres, you will for sure have n-gons remaining. You’ll see the best bevel results with quads only

Ok thanks so I better find another process.
Do you happen to know if there is a way to use an object as a selection tool?
I mean select all the vertices on object 1 that you are touching with object 2?