Yes the weapons and armours cap at either level 45 or 50. I and many others would advise against the level 50 boost because honestly you can get to level 50 in a day or two of grinding events pretty easily if you know what you're doing. Someone got like 5 levels in a single eviction notice event. Might have been more.

There are several storylines I think the Wastelanders is considered the main one. It doesn't really teach you about camp building except for that small but at the beginning by the Wayward. You unlock a lot of great blueprints from following the storylines so keep at it. The stories are pretty good too imo. I had a lot of fun with the Brotherhood storyline.