I have been playing with deleting files/repair, delete/run, delete/restore from bin. I can delete these, and run a game in progress, if deleting between game restarts. In addition to localthumbcache.package, which I'll relist for completeness:
In ../Documents/Electronic Arts/The Sims 4/
localthumbcache.package
/cache/*.* (it will be regenerated)
/lotcacheddata/*.* (created when you edit a lot, maybe when play on one)
No repair needed, just delete. I haven't done more than a couple of days and 3 games worth of testing (a bit of editing though). But those seem safe enough for me so far.
I started playing with this when my games developed the stuttering I used to get in Sims 3 with many files. I don't think I had enough in them to cause it, but it didn't hurt. My issue seems to be the Tray folder (library on local disk). I'm going to add a post on that as it isn't deletable like a cache.