266 folders in your own user/Library folder? I have 85 folder in my user/Library. The folders created in that Library folder would depend on what apps you use, I suppose. 266 is probably not crazy. Folder names can often help you decide where those folders come from (what app is involved)
Here's what I might do in your case:
Open that Library folder, and show in List view. Sort by Size, so the largest size is at the top of the list. Usually, that will be one of three: Application Support, Containers, and Caches. Mail, and Safari are also usually in the largest on my Mac.
"culling" is not too likely, unless you are completely confident that you would be removing files and folders that are not used by anything, and that you know you won't be needing in the future, and that you also know that you are not removing folders and files that might be used actively by apps on your Mac.
After sorting, what are your largest 5 folders?
One folder that actually is pretty easy is the Caches folder. If you see that at the top of the list - largest size folder, you
can almost always feel safe in deleting large folders inside that Caches folder. They are ALL temporary files used by your apps, and the system for your user only. You can safely remove files from that folder, or even drag that Caches folder to the trash. Your system, or the apps that you use will create new files and folders in Caches when needed. You may want to be aware that as new cache folders are created, you might experience (temporary) slowdowns while those files rebuild, but that might not be noticeable in most cases. So, you can always clean up that folder, even in use. I usually restart after cleaning out the Caches folder. Be sure to empty the trash then. The files in the trash still take up space.
What else is taking up space in your Library folder? (Again -- don't just grab random large folders to drag to the trash, unless you are absolutely confident that you know what you are deleting. You may discover that you have a folder full of data files that one of your apps uses, and deleting some files may mean that you have to reinstall that app, so always take a moment to "think before you trash!"