A: Hello Holsen,
125GB is a lot and it is very likely it will be more than enough for a regular website.
Anyway, if you want to be sure you can buy 2-3 codes and start using ShortPixel Adaptive Images.
After 1 month, you'll know for sure how much you website needs in terms CDN traffic and you can refund 1-2 codes if you feel they are too much.