This is more of a PSA than a question per se, since I figured it out, but I wasnt sure where to pop this info, was either here or Support
Sorry Jannies.
TLDR Increase PHP Memory once you have X amount of tags
I ran into an issue on my site where the Tag page became unable to render. I assumed there was some conflict with other extensions, such as the Categories one, however I eventually... and i mean EVENTUALLY figured out that the PHP_MEMORY_LIMIT was too low at 128M, so I have increased it to 256M.
I used a docker image for the site so I had to figure out what I was doing.
Just edit the flarum.env on the host machine and include PHP_MEMORY_LIMIT=256M. Then restart the machine.
(I did try restarting the container but the changes weren't going through)
I hope this helps someone