Can anyone help a newbie with the best rom to flash?

Oh, so I have an Xperia tablet z spg321 Lte on 5.1.1
It's driving me nuts as I need root so that I can use keymapping and six axis apps for remote play. So far I have figured out how to unlock the bootloader using flashtool. Now I need to know what the best rom to flash is, preferably pre rooted.
Also it would be good if the rom was ftf format for use with flashtool, as I don't feel confident enough for command line flashing. What I have in mind is something that is just a straight easy flash and done. Can anyone advise me and point to me to where to get the rom files.

Newbie Question - Does Rapid/Quick Charge technology only work when the phone is on?

On all my previous phones, I used to turn the phone completely off when charging.

Did the same for my first 5x charge up, but noticed after 20 minutes in phone-off-charging-state when I checked the white battery icon, it wasn't showing it was filled up at all. Strange.

So I turn the phone on, it shows it's charging, but only got to 5% from a completely drained battery.

This didn't seem right, so I left the phone on for 20 more minutes where it specifically stated "rapid charging". It shot from 5% -> 31%. Let it keep doing it's thing and 20 minutes later it went from 31% -> 75% with an estimated 23 minutes left. Impressive if it really would go from 5% -> 100% in about an hour.

So, does rapid charging only initiate with the phone on? Or, is that first 5% just a natural long charge area of the battery and the phone woulda hit high-gear-rapid-charging if I left it off the whole time?