They like to make things confusing, but basically there are 2 kinds of supplemental Medicare plans. One is called medigap and is offered through various companies such as USAA. What my husband and I have is called Part C, a supplemental Medicare insurance plan and ours is run by Aetna. It is an HMO with prescription drug coverage. We never have to deal with Medicare directly. We can go to any doctor who is on our plan and we have zero copay for primary care visits, $40 to see a specialist.
Many Medigap plans have premiums but no copays. Our plan has no premiums other than our basic Medicare premiums, but we do have copays for specialists and other things. We also have copays for some prescriptions. Some of the simple, basic ones are free.
What really helped me figure all this out was going to a presentation by our supplemental plan explaining all their plans and benefits.
Supplemental plans tend to be local, so if you move out of the area, you will need to find a new one. Medigap plans follow you no matter where you live, but you do have to find doctors who take Medicare when you get there.
The Medicare website has ratings for supplemental plans in your area based on user reviews.
Hope this helps a little. There are so many details and different plans, that it’s difficult to explain it all here.
I think you meant to use the term “Advantage plan” instead of “supplement”.
Supplemental policies are the same thing as Medigap policies.