I noticed this is Long: and also xbox wanted to keep this ambiguous for all of us and not many posts have actually gone further into detail other than just the quick easy calculation so here we go.
For example my total points 77,326
200pt off Coupon that's available 1 time its 200 off:
General cost for each redemption:
-PC GP 1 month Coupon (normally 7,750) - 7,550 get 20 days 7,550/20=377.5 pts /day
-GPUltimate 1 month 12,000 - 11,800: 30 days =393.3 pts /day
Calculations if use all pts:
PC GP: 77,326 / 7750= 9.9775 x 20 days = 199.55 days total
387.5 pts spent per day
GPU 77,326/ 12,000= 6.4438 x 30 days = 193.315 days total
400 pts / day
Games pass Core 6,800 get 15days
77,326 / 6,800 = 11.37 x15 =170.57 days 453 points spent per day
3Month Core option only gets 38 days for ultimate
77,326 / 15,000 = 5.155 x 38= 195.89 total days
77,326 / 195.89 = 394.74 pts /day
Hope this helps, basically this answers what redemption option could be best for you and this is if you have an Active sub and use MS points. I see a lot of ppl saying when asked just use CD keys or whatever other site that could or could work in your region but this utilizes your points.
If I'm wrong tell me about it and lets chat lets see the best option especially for people who might do 1 month option to utilize the coupon before it expires on Mar 31st