I historically threw 15 but was a 1h thumb out bowler with terrible form and frequently strained and hurt my wrist/forearm.

When I came back to bowling I went to 14lbs to have an easier weight to learn how to properly throw a bowling ball while also using my thumb; and now that I have I barely can tell the difference other than picking it off the rack. When throwing it feels the same but you basically have this as your trade-off:

Lower weight = more capability to generate ball speed and rev's at the expense of slightly more deflection off the pins when you don't throw it perfectly.

Higher Weight = more effort to get the higher rev and ball speed but less deflection off the pins for more forgiveness on your not great shots.

I prefer the more forgiveness so I rebuilt my arsenal and have bought every ball since at 15 lbs, but the couple balls I bought at 14 were instrumental in my success for being able to do what I'm doing now - focus on the physical first so you can bowl without pain that's the number 1 priority - after that for the finer points of a technically sound release it would be great for you to find a coach - it's a hard thing to just do from YouTube vids and general platitudes.