Hi jimbi, how did you got the oficial 772 version? Via OTA or do you have a download link for it?
Myself I had a Lenovo phone for the last 4 years, with original ZUI rom, but heavily debloated by me so I did know what packages are not essential in Legion Y70.
I got root via Magisk
I got a RW system partition via LeBigMac programs
I heavily debloated the system partiton (464 apk and libraries deleted)
I replaced keyboard app, Phone app, SMS app, Launcher app, CALC app, Calendar app, Contacts app with apps from an old Lineage version and after that I installed AFWall firewall.
The phone just flies! And the battery runtime is extremly long.
I plan to not use the fast charger to extend the battery life.