All Medicare Supplements were standardized in 1992, in June of 2010 they were Modernized. Insurance companies that are selling Medicare supplements, all sell the same Modernized plans. You can go to any doctor any hospital anywhere as long as they accept Medicare. There are no networks. The benefits in the Modernized plans do not change unless Medicare changes them.
Depending on the Medicare Supplement plan you have, with Medicare and a Medicare Supplement, you may have 100% coverage. There will be a premium charge for a Medicare Supplement, but have few additional out-of-pocket expenses. Rates may vary depending upon age, state, health condition (past and present) and medications talk to an agent today to compare plans.