Necroing threads... and necophilia! are not against the guidelines. I checked!
I tested it last night just a bit (and then stayed up way too late looking for nicer underwear replacers, shh....)
As the author warns, debug mode is on by default, I didn't look into how to turn it off but it certainly did spam papyrus. Most of the errors seem harmless, I was getting worse/more errors from other mods (need to look into those...)
Cleaned out a few camps of forsworn (I don't understand how this camp managed to spawn 100% female forsworn, it was like 10 females and two were pregnant o.O), and it worked pretty well. Note that the underwear did not show up under their armor - so if you did an upskirt (surprisingly easy with forsworn armor) they were nude, but once you removed the armor they had the underwear from this mod on. I didn't have issues with script latency or any behavior that seemed like a mod conflict, which I was a bit surprised by tbh.
The underwear is lootable so if you're the kind of person who does "loot all" and throw away the trash later, this mod won't work for you at all.
So... for my modlist, this would be a "yes". I generally use nevernude bodies anyways, but was looking into underwear mods both so I could use nude bodies, and because a few of my mods (bijin, males of skyrim) come with nude bodies and this seemed like an easier answer than trying to replace every body they come with with a nevernude variation :P (I mean, I don't INTEND for jenassa to lose her armor but when you're playing with outfit management things happen, y'know?)
There's an alternate mod I looked into on loverslab (not sure if ok to link here, it is NSFW), which I didn't test. I may do that later though. It needs a bit more setup - you have to add actual underwear from other underwear mods to your inventory, then fiddle with the MCM quite a bit, to get it to distribute the underwear, but the plus side is that it can randomize undies and not just have the same one on every single NPC.
If your goal is to make sure there's no genitalia in your game, ever, you should just use the nevernude version of the body mod you like. Literally all of them have one, some like CBBE have multiple options. For STEP and the guides hosted here I think that would be the safest option, if a body replacer is ever wanted.
If your goal is m'mersion, and to be able to have nudity in some scenarios but not others, then this mod may suit your purposes.
I'm still curious if others have tested it more extensively.