Project backstage.... Options, Display, what is the size of your local cache? Clean it out regularly, the more maps with lots of data, the bigger the display cache, Cleaning it out is only a temporary solution. Too bad about your org. going on the cheap for local drives
@KoryKramer 's recent performance doc may have some other info
Troubleshooting Performance Issues in ArcGIS Pro - GeoNet, The Esri Community
PS
obvious ones like garbage bin, any temp folder, especially those in your user profile that may be created/used by Arc* and any other apps
... sort of retired...