This measuring jig fits between the top of the z-motor mounting plate and the bottom of the x mounts. When it fits about the same on both sides you should be good to go! -Alternatively you could make two of these and lower your z until it bottoms out on both.
My printer as it is setup up currently rarely needs any adjustment if the bed is well leveled once. I just do a quick 4 second check with the jig after homing and about 10% of the time I may need to turn a z motor a click or two. Good enough for me!
I feel I should note that one simple thing that I changed on my Tronxy P802E that made a BIG BIG improvement on getting a consistent bed level was to replace the horrible acrylic bed undercarriage with a solid aluminum one. https://www.thingiverse.com/thing:2545713
Flip the model flat on its back. Then scale the length to your needs. It is 100mm long to be easy to scale. My setup happens to require 77MM. So I would scale in one dimension to 77%.