I think if you had hit a limit of any sort, the game would CTD as soon as opening, much like what happens if you start the game with a missing master. I dont think you would be able to play at all because the game would refuse to load 'too many' mods. You must have a conflict. Also the missing texture things means you either installed something improperly, or someone who made a mod forgot to include textures or set the path wrong.
One huge question I dont think anyone has asked yet; Did you slowly build up to this 189 and it broke suddenly now, or did you installed all of these mods at once and its not working? You should never install more than a few mods at a time because it makes it very difficult to locate a problem mod in the case of an issue such as this.
I've fixed the problem myself as I said earlier... I know the usual thing people do is blame user incompetence. That's justified 99% of the time. However I'm wondering at this forums level of reading comprehension at this point. I've written several things that should have ruled out broken install paths and conflicts alike.
Here's the thing... I didn't have to delete any mods in order to solve my problem. All I had to do to solve the problem was create a merged plugin file.
You know, just to make extra sure what I've seen was correct on this issue, I created two separate merged plugin files. Each with different esp's inside. Both had a set of 21 esp's in them which brought me down to 189. Both solved my problem... it wasn't a matter of which mods were in the combined .esp, it was simply a matter of getting them down to that number.
To further test whether or not it was indeed simply the number of mods I was having to load instead of a conflict, I took those same merged plugin files and instead of having 21 esp's in them, I tried them with 20 instead (thus bringing me to 190 total plugins). When I did this, regardless of which set I used, I again had issues.
To even further test this issue, I then re-inputted the mods I had taken out into the merged plugins and took out a different mod instead (again bringing me to 190 mods total). Yet again, crashes happened.
What I'm trying to say is, regardless of what mod I use, as long as it's the mod that brings me over 189 mods, I get issues.
It took only the smallest mod changing only one record being enabled to cause all sorts of problems (one of the most curious of which was the inability to use my Escape key)....
While a large mod caused the exact same problems.
I know I'm not a good writer, and this is such as odd occurrence so it's difficult to put into words.
Another thing ruling out improperly installed textures/meshes or anything else was the fact that it affected every NPC -- it even affected Enhanced Blood Textures. I have many mods editing many things, from raider specific ones to power armor specific ones to blood specific ones... they wouldn't have all been installed incorrectly... and if they were... they wouldn't be working now.
I did find in all of this one horribly made mod that if you're truly interested in looking into as a possible cause of this problem you can try out yourself. All it was supposed to do was edit one of the generic food types into Twinkies instead.... I was wondering why it needed a .ESP file for this but I went with it anyway.
Turns out this .esp file was loaded with all sorts of crud it didn't need. Scripts for bobbleheads was what tipped me off, because I started a new game and I noticed that when i clicked on a bobblehead (I have FWE installed), the message that pop up informed me I was receiving a bonus of 0 (instead of 5 for the medicine bobble in the alternative start shack)... and the bobblehead stayed where it was instead of going into my inventory.
So I loaded up all the new mods I had gotten recently in TESedit and did a quick search with the keyword "bobb" and I noticed that the mod from http://www.fallout3nexus.com/downloads/file.php?id=13402 actually had those scripts attached for some reason. This was the post-war one I believe.
So maybe it was also the cause for all of my other problems....... but I doubt it because of everything else I've written. As long as I was underneath 190 mods, even with this Twinkies mod checked ON, I wasn't missing textures or having crashes and I could use my Escape key.