I am a little over 5'-10" and my eye level is 65" in bare feet. The top of my trains on the highest track is 54" I find this works for me but would not want it any higher; the upper passenger yard is 6 tracks wide and that makes it harder to see across. Were it just one track near the edge it could be a couple inches higher.
My wife's eye level is 58" and the upper level track is too high for her to look at comfortably. She cannot see the trains on the passenger station tracks beyond the first track.
Everyone's preference on how they want to look at their layout is different. I prefer a slight downward view but many like to have their track near eye level. I think that because of the depth of the reverse loop portions of the upper level having the layout plywood top at 50" would work for you. I would recommend a lower level table height of 35" as a compromise of getting barely adequate separation from the upper level and also not having the lower level too low.
I found testing these heights by drawing lines on the wall did not work well. The lines seemed low. When the room filling layout was installed including scenery that varied from 3" to 18" above track level plus the backdrop that extends to 7' everything seemed much higher and I am frequently looking slightly up at the scenic elements that are part of the layout. It became a very immersive experience to be in the train room.
