Yes I did try your A9 kernel again and it did not go well, I am back on the old A8 kernel F800K. Seems much saferYou tried A9 kernel again?
Are you using the latest TWRP? Use 3.4.x.x. Check my AFH account in the Pie Rom folder.
I really think while you are at all this you should just install my new A9 Rom. And I will improve on it with tweaks. It's way better than A8 as it is.. And performance is not the only concern. Apps are likely to be more compatible with A9 meaning some apps that were troublesome on A8 are not on A9.
Then again make up your own mind, but I have the same device as you as I'm pleasantly surprised by the Pie update. Major updates often slow a phone down but not in this case. Clearly software improvements in the system. The only reason I can' think of not to update is if you need the carrier apps which are bloated from my rom.
TB is still active and works the same as it always did. Personally I have always had problems with it but I don't know anything better. Restoring from a major update from a lower one might not go well either. It's good for restoring the apps itself but adding back it's data i.e. your settings, log-in settings, often doesn't go well.
I'm using TWRP 3.5.0-9 I think it is called. I think I will stay with me Android 8, I know it from years of use. At least for now I think it will do.
Might just as well buy Titanium Backup and give it a try - and hope the developers come back if they have left it. It seemed to work with the new mobile, although I do not know as it died on me in the process of installing applications with my first minor drop with the mobile.
I have another Application to look into, Lucky patcher, if it can remove the spying from some of the apps and such. Would be nice, I have so many apps that sends info to whatever accordign to TrackerControl.
If anything I would like to try Lineage A10 - that would be close to my new mobile I think in build which also runs A10.