Out of it for a year, now I'm looking for advice and opinions.

I got this SM-P600 last year for my birthday, I shortly rooted it then installed a ROM and went on my merry way.

There have always been a couple nagging issues with the rom, infrequent random restarting and blanking out my lockscreen and homescreen wallpapers.

Its on the ND2 bootloader but the "fingerprint" says NH3 release-keys, so NH3 firmware I assume.

It is rooted, twrp 2.5 or 2.6 I think.

I just want to get the firmware updated and install a stable rom on it since the restarting and wiping away wallpaper is really getting on my nerves lately.

I have been out of the tweaking and modding environment for almost a year now and I don't know where to pick up again.

So I am looking for advice and opinions.
I need to find a firmware only page, or a way to update the firmware easily, or am I missing something here?
I'd like to hear about a couple roms people out there are using, why you use it and how long?
I'd like to know if I need to have the bootloader and firmware be the same version and if that might be why I am having issues.
Can anyone point me to the right place?