Proper way to implement CB Subs with upgrade options

I've found where the templates are installed (/components/com_comprofiler/plugin/user/plug_cbpaidsubscriptions/templates/).
However, I'm not sure at all which folders/files pertain to which part of the subscription process, or what specific block of code would need to be modified to hide those buttons for renewal/cancel.

Is there any documentation anywhere that explains what each file pertains to (or any other help in creating custom templates for CBSubs)?

Unfortunately, as noted several times before, your solution doesn't meet the requirements:

All the top level plans are exclusive as well so they can only ever be subscribed to A, B, C, or D.

We need to have:

(A or B or C) and/or D

D needs to be completely 'independent' of A,B,C. So setting 'exclusive' at the top level doesn't achieve the site needs. It prevents the user from subscribing to 'A and D' (or 'B and D' or 'C and D').

You mentioned:

do this through the template .... adding code specific to that plan id

Can you give some instruction on where/how to do this?
I think this looks like the only solution.

We need to have:

(A or B or C) and/or D

D needs to be completely 'independent' of A,B,C. So setting 'exclusive' at the top level doesn't achieve the site needs. It prevents the user from subscribing to 'A and D' (or 'B and D' or 'C and D').

Please see my reply regarding "Plans A1, B1, and C1, are just copies of Plan D and made set as child plans to A, B, and C.". A, B, and C would have a child plan that's non-exclusive which is an addon plan for A, B, and C. It'd give the same benefits as Plan D. This covers your usecase of A + D, etc..

Can you give some instruction on where/how to do this?

We don't provide custom coding assistance. It'd probably be a PHP if statement in maybe the below.

components/com_comprofiler/plugin/user/plug_cbpaidsubscriptions/templates/default/productusersubscription/default.php