Use the compare page to check the details on a few models and see which changes between them will actually interest you, and which specifications don’t change between models
I have an iPhone 12 Pro
My key decider when deciding on models has been the camera, and which versions have true differences in lenses & optical zoom as opposed to the further options in the software
The Pro max would have given me another step in optical zoom, but be a much larger phone
I have large hands but did still struggle with the keyboard on a larger model in the past, this doesn’t matter if you type two handed but typing one handed took my thumb on some long stretches
The 12 Pro is about right for me one handed (though in its case most phone stands struggle to stretch that far. I use a rugged case and if I want to use my wireless charging car phone stand I need to take the phone out of its case or spend a while forcing it to go in and align with the charger)
For Bluetooth - all will have this, but if you never use it then it can be disabled. Bluetooth does give some less obvious features such as Apple Maps ‘show parked location’ via Bluetooth recognising the last time it detected my car stereo
Note that ‘Retina’ is used by Apple as branding for the screen pixel density, and I assume that you are referring to facial recognition.
The iPhone 8 range are the last with a touch ‘button’ activation, so any upgrade would be to facial recognition. This saves a second or two without the need to press and type in a PIN, though the PIN remains for when recognition fails or on restart/software updates
Have a run through the comparisons of a few models for the specs that will actually interest you and if possible get hands on with some different sizes :
www.apple.com/uk/iphone/compare/?modelList=iphone8,iphone12