The problem is omniscience. No one has it.
Lots of rabbit holes. Some well meaning, some mercenary.
So take one thing at a time. Question everything. (I know you have other things to do) Don't hold any conclusion with a tight fist.
Start with calcium that will lead to K2 and D3.
Once you decide, it settles into routine. Then you can adjust here and there at leisure.
If I were osteopenic, I'd look closely at the Estrodial Patch.
It is easier to retain bone density than it is to regain bone density.
Best wishes for your bones