My question is can I still use coins or bills to pay the fare if I don't buy a QuickCard. If yes, what denominations/types of coins are accepted in the turnstiles? Thanks in advance.
All coins (except pennies, and including the dollar coin) are accepted. I think all denominations up to $20 are accepted, but check with someone on that because you'll get a whole bagful of change with it. Yes, the PATH QuickCard machines does have 2 trip QuickCards (which are at NWK, HOB, and elsewhere), which I recommend you get if you can. Certainly better than waiting in a line with people busy fumbling for change.
One thing I advise is that if you're a 'hit & miss' PATH rider be aware of how many trips you have left if you buy a 20 or 40 trip card. After these expire, there's no way to get the remaining rides back. Much less, PATH doesn't even have booths to negotiate your expired card, as you can with the NYC Subway.