Yes he should get at least 150H/s with ZEC.
Getting 20H/s on nicehashminer maybe it's not fully tested and config isn't set up properly but 150 is unreal (possible with some cracked bios or something maybe) (exp 47mhs with little overclock, after watercooling we can go for more overclock and maybe 50mhs+)
I found that mining EXP results in a faster speed however you usually make less with the coin so in the end it balances it out. Just a waste of electricity
Don't worry we have free limited electricity so that's not a problem
You should use the Claymore miner, it is quite fast in the old cards like the 7970, 7990 or 280x.