So I'm deciding if I should stop doing let's plays of custom stories and...

[WALP]

given effort, the author will at the very least love or appreciate your review. you could probably also get a few more people watching by linking the review in the thread of the mod, given the authors permission.

It depends quite a lot on the quality of your videos(of which I have watched none), but I think that if you can keep it up with the released and have them be relatively close to the mod releases you might be a able to build up a decent audience of people using your channel as a way to find mods and see if they are something they would like to play.

You could probably also gain interest from people who have played mods you have reviewed, and wish to share their thoughts on it as well as see what others(you) thought about the mod.