Medicare has traditional fee for service [FFS] care. A; Hospitals, (automatic ), B: 'doctors' D; drugs. B & D are optional most get B & D. You do need to register for Medicare before it would be in force.

Supplemental Insurance: coordinates with A, B & C depending on one of the 10 state approved 'Medi-GAP' policies. Jeff mentioned there may be problems getting insured (Health) with diagnosis of Prostate Cancer. I believe he is referring to these supplemental Medi-Gaps.? I do not know how the Affordable Care Act [ACA'] anti-discrimination to prior illness protection applies if at all. Medi-Gaps often pay the annual 'in patient deductible' for 'A' costs., it typically pays for co-pays of 'B' costs. My brother has an AARP (UHC) supplemental Medi-Gap which pays 80% of his 20% B co-pays or 16% leaving a 4% residual responsibility.

NOTE: Medicare is the final payer. If a spouse is younger and still in the workforce with generous group health insurance available to both of you: double
check the added costs of the spouse and review coverages carefully. Group pays first, Medicare A, B, D next. The various plans are stacked in order and after consideration and payment if any the claim is automatically forwarded to the next payer if any.

Medicare Advantage is the managed version. Although cheaper for the time being because of federal subsidies it limits Out of Network care options, e.g., only exclusive providers [EPO] or it cost too much for non-preferred docs.[PPO]. With traditional FFS Medicare plans you could go to Mayo HQ to get a choline PET-CT scan if useful as it is the only place that has it. Forty years ago I knew someone who went there because he had FFS traditional Medicare. At the time they were the only place to use 3D CT fabrication of hips not the modified off the shelf versions. He was young for hip surgery, every advantage was helpful for him to avoid early revision with the unique duplication of his anatomy.