I have upgraded lately from OE 6.0.3 to LE 7.0.2 on RBi B+ using tar upgrade method. Yesterday RPi 3 came to me so I made an upgrade again as LE wiki advises. All went quite fine, the system boots up and shows COnfluence as it should. No I'm discovering how it works
And after above upgrades are made I have config.txt from OE 6.0.3 thanks to this my HiFiBerry Digi+ worked OOTB not sure what else did not get upgraded