I too am retired military with 80% VA disability, but too young for Medicare! (58!). I have Tricare Standard (or whatever they call it today), with a supplemental policy from Military Benefits Association. Since I don't pay a premium for Tricare, I don't mind the annual premiums. My supplement covers Tricare's deductible plus the cost share up to Tricare's maximum allowable (same as Medicare).
I generally use the VA for general health checkups and VA disability issues, but I use a private clinic for occasional minor illnesses. Although my disability rating is for back neck, hand injuries on active duty, I chose to use a Non-VA provider for back, neck and hand surgeries because of the wait times for treatment at the VA. Recent surgeries and short hospital stay was 100% covered by Tricare and supplement.
My only issue with Tricare is that I have had to fight with them (including calling Congressmen) to get treatment outside the region where I live
. I live in Missouri (TriWest) and the Doctor was 300 miles from home in Nashville (TriEast).
That's why I have Tricare Standard, so I can go anywhere I want to! I won the fight, but shouldn't have had to go that far!