As for your questions about which rom to flash. I was on 10.3 and flashed 9.5.23 weekly. I've had not one issue, all is running smoothly. There are lots of threads from people having problems but i have never had an issue. Im sure you will be fine. You have Twrp so do a backup and you can always revert if you F*c* it up somehow . Im watching your post if you get stuck.