My advice on straps, based on decades of windsurfing without any ankle injury:
- the more rigid the better. But try to use regular sized ones, not the wide ones. Also simpler straps are lighter. Be wary of wide straps that tend to twist more (added leverage on the side)
- have some way to prevent them to rotate around the screws. The best solution would be to have 2 screws per tip, as with sailboards, but no SUP board use them. So use steel plates with teeth and screw hard,such as:
www.24-7boardsports.com/starboard-footstap-anti-twist-washer/DaKine has some anti-twist system with plastic plates above and below the strap, but I find them a hazard for the toes.
- Be aware that the pad will compress with time, so you should check the screws before each session. There should be absolutely no rotation of the straps around the screw.
- the foot must slip in, and especially out, very easily. This means your foot must not get in too deep. Ideally the junction between the toes and the foot should be protuding by 1/2" - 1" max on the other side. Too little and you will not control anything, too far and you may not get out easily.
- The pad grip will tend to keep your foot in, especially soft pads where it will "sink in". This means we must avoid having the strap pressing downwards, locking the foot into the pad. The solutions can be to use an incompressible pad (hexatraction),or have the strap push more on the sides of the foot than on the top: this means have very narrow straps that block the foot more than the side than the top. It will also help the foot rotate on its side on wipeouts and get out easily.
There is a common misconception that a wide, open strap is safer. It is the opposite.
Boots are a pain with straps. Try not to use ones with grippy soles, or you wont get out. Straps on top on the boot may also lock the foot in it.
Some images:
Wide open straps like these below are extremely dangerous: the solution is to use closer screw holes: ( plus they seem to twist)

This is excellent :-) narrow straps with a very round opening. Note the pool noodle bits to keep their shape between sessions:
(The front strap has not enough angle in this photo, I added some more since then for more comfortable paddling)

This is bad: you can see they are not screwed tight enough, or the screw plate is not rigid enough: the strap twists: