I wonder what RAM size you have - here it is 8GB
checked memory usage: Avg 2.4 GB of 7.9 GB
Another thing worth mentionig is that I do not use is e-cloud / use my own Mail/Caldav/Carddav
The apps I use the most are browser, (K9) mail, Calendar, Signal, VB (Banking) app, password safe
Nearly forgot I use a non standard Micro G (for contact tracing) - shared by @Cabnedor FP4: Install of microG Exposure Notification fails - #9 by Cabnedor
And all the issues (Aegis, OsmAnd) work perfect here on my FP 4. had not a single crash since I installed
maybe any of this can help