That is not true, at least completly. The Hz DOES matter, the RGB just corrects the colour problem, the console will still output 50 Hz with a PAL game no matter what cable you're using and if your TV doesn't support 50 Hz then you will still get a rolling picture.
For the benefit of the PAL folks--there are no TVs here that run RGB, hence, no TV solution he is ever likely to see will run 50 or 60Hz RGB. RGB monitors on the other hand routinely sync easily--even ones made specifically for the NTSC market going way back have been made with this in mind.
I understood that the original poster has rather old NTSC TV that does NOT have RGB input... ?
Uh, yeah, and I just gave him one real good reason to GET an RGB monitor, capitch? We routinely get questions from folks here asking "why do you go through all the trouble to do this?" Well it's not that much trouble, if you do it right you may only need to set up a workable solution once, then you can play til your set up dies, and look at all the problems it solves on top of the inherent quality?
Other stuff: the Pro Action Replay is really just that, a GameShark-alike that allows for setting modes including regionals. Not really a mod-chip at all. The real mod-chip dev in the past five years has happened for the PS2; they are still out there, but it is hard to get good information on serious mod-chips for the PS1 these days. I recommend DMS4 Pro in the way of PS2 mod-chips, it pretty much does everything you need automatically but includes options to force video modes.