I think testing is essential so you don't encounter conflicts or crashing. I ran into the Children of Ug-Qualtoth area, made sure it loaded, ran blindly around for a while, then exited. I am compiling a load order of non-crashing immersive mods with which to start a new game and do a let's play. So I have to make choices and run around a loooot to determine if a settlement will crash over time or if it is stable for me. I looooove his settlements, however, my xbox can only handle 1 or 2 of them due to high demand on my CPU and graphics. I have often found things that conflict, or crash altogether due to my OG xbox being unable to handle the strain of the overwhelmingly amazing area or item.
Especially with new worlds, settlement overhauls/redo's, and item mods, you have to visit there and use/build the items before you play a real game. I test each mod, area, item, npc, thoroughly and run around in it or use it for at least an hour before I consider something lag/crash free and move on. I make a fresh save once a mod is officially accepted as part of my master load order and I move on. I have added and removed about 50 mods so far in my 'testing' phase.
