Can't compare the Panasonic evf to Sony, but judged against any of my Fuji cameras (maybe except the X-E1) its very poor
I have had the GX80 and now got the GX9, knew what I was getting with the latter, but doesn't get over how ropey it is
Very hard to get sharp detail no matter what adjustments are made, never seen the tearing effect, but its still less than great anyway.
Rest of the camera is excellent, so price you have to pay, every camera has its weaknesses and on these two its the evf