You can only use it in person to reduce (by $25) what you pay at the hotel, so you can't use it on totally prepaid rates.
I don't even understand the rest of your questions. You can only use it to reduce (by $25) a Best Western stay. The rest of the stay is paid (at the hotel) however you would otherwise pay for any Best Western stay.
So the $25 GC doesn't do anything except reduce by $25 what you have to pay for that BW hotel stay. End of story!
Worry first about whether there's any stay you want / need to do (before the gift card expires) where $25 will actually save you money. (Choosing to stay at a $150 BW just to use a $25 off card, when you could have stayed at another equally-good hotel down the road for $80, is not "maximizing" IMHO.)