I will see about getting Pathfinder updated, but yes EX4600 only runs ELS CLI. You do NOT need to run same code on EX4500 as on EX4600. Actually it would be very doubtful you ever would. BEST choice on EX4500 is 12.3 or 15.1, while for EX4600 it is 14.1X53 and then some 17.x. You only need to have same code on switches when in a VC or VCF configuration, and EX45xx/EX4600 can not VC/VCF together.
As for you config best choice is to first get EX4600 on code version you want to run. Then on EX4500:
show configuration | display set | no-more
and then get a copy of this output
run output through ELS Translator
take ELS Translator output, and load this on EX4600; all passwords should remain the same.
run commit check on EX4600 config. If any errors fix them. Take a look at config and see if looks correct.
Good luck.