I have the green biowaves case for the FP4. They are hard bio plastics and very snug. So getting the phone out again takes quite some effort. Good thing is, you won’t have to fear that the phone could fall out the case, like it can happen with the official one. But they are also very smooth, a little too smooth for my taste. Happens that the phone slips off my hand, or easily slides on smooth surfaces. Apart from that, I actually like the design and that they conceal and protect the camera bump.
So if you want fair cases for the FP4 you can choose between the official very loose but rubbery and flexible, or the biowaves very snug and slippery hard plastic. I don’t like either unfortunately. I liked the official one in the beginning when it fit better, but it wore out quickly and now doesn’t fit right anymore.
I would hope for the official FP5 case, that they figured this out and that the cases keep their form longer and fit the phone better.