AF fine tuning
and found that at 2.8 lens focus perfectly with no shift at all but at 1.4 there is some front focus so adjusting it to +10 I can get sharper results.
AF always takes place at f1.4 with an f1.4 lens
+10 is a significant shift - enough to show up in the viewfinder with reasonable eyesight, and far greater than occasional focus shift changing aperture.
Are you saying the viewfinder (which views at f1.4) now looks sharper?
99% of photo equipment is good or very good. The main thing to do with it is to learn to use it well.