I bought my wife a FP 4. I’m quite impressed with it. I currently use a OnePlus 6. My main factor for choice was ease of rooting. Root access is mandatory for me. I am considering a FP for next. I need Magisk and preferably with twrp. Am I likely to be disappointed?
No, I don’t think so. Rooting is quite easy using the ideas from the threads above. I also had in mind I would need a TRWP on my device besides the mandatory admin permissions. So far I haven’t missed it to much with FPOS.
An other idea would be to install LinageOS 20 that comes with its own recovery. Something I have not yet tried myself.