The human eye perceives colors relative to their surroundings, so a black pixel next to a white pixel will look blacker. You can exploit this effect to enhance the perceived contrast ratio. How well this works in practice varies.

https://en.wikipedia.org/wiki/Checker_shadow_illusion

This, and in general setting LED brightness to minimum necessary to get target brightness with fully open LCD, taking into account interaction of nearby LEDs (light from one LED spreads to adjacent cells, thus you could minimize brightness of boundary LEDs even farther).

I read the papers - it can't, they just seem to have novel ways of controlling the zones available. I supposed the smaller the miniLED array the more control you can have over the zones and the better it works. But there doesn't seem to be anything that really solves the bleeding issue.