It really comes down to your own personal concerns on safety. As with everything else in building a car, there are compromises. You can make the best impact structure in the world, but still die when something small punctures the floor. If main criteria is protecting from other vehicles while not braining yourself on the roll-over protection, I'd go for a 4pt rollbar with "door" bars and 3pt or DOT 4pt belts (not race harnesses).
Couple of points:
-necks/backs stretch a LOT in crashes. Things are closer than they seem.
-proper rollbar padding will not help the helmetless head (it's very dense)
-most people build rollbars/cages too short so they don't look goofy. Myself included to be honest (if I'm going to die, I'm going to die pretty damn it!)
-you can't use head/neck restraints without a helmet. No point saving your head if your neck snaps. You do NOT want neck whiplash. I can promise you that from daily experience for the last 20+ yrs. If you strap yourself in tight with race-harness and get into a frontal collision you will damage your neck. DOT belts stretch to help.
https://www.youtube.com/watch?v=g40YatgE_CECheers.