DrYak and aspergerguy thanks for nice answers!

I got few questions still:

1. How about jolla or community make to sailfish x use 4k resolution option in default cam app or making new native app. I tested that 4k resolution option in opencamera called app in play store and it's works well.

So I can at least download it for sailfish and hopes it works on sailfish.

I think Sony's overheat message is ******** and I can record video even 4k so long as I got space...

2. Oh so there is no software limitation for Uhs standard, only kernel affect. That's nice for sailfish it can be as fast as android.

Now I know it's not waste of money to purchase Uhs marked sd card for my xperia.

Btw anybody tested 256gb sd card in xperia x?

Sorry I'm pretty ignorant details of phones.