I wound up solving this problem. The issue is that the lv_conf.h file doesn’t actually set a bunch of the memory limits, or the logging or a few other things for the library to work with, these limits are hard coded into the library file at compile time (at least when its built in Yocto).
The solution that worked for me, was to go into a file in meta-openembedded/meta-oe/recipes-graphics/lvgl and modify a file called lv-conf.inc which contains the settings that get injected into the lv_conf.h file during compilation, and set LV_USE_LOG and LV_MEM_SIZE in that file.
I’m sure there is a better way to do this with bitbake overlays, but I just wanted to make sure if anyone else comes across this issue they have a starting point to solve it for themselves!