Not much of a tv video tech, so I am not sure what they are referring to,
just an HDMI-to-RGB cable or will I need a converter box?
As I mentioned previously, you will need a converter box. No "simple cable" will work for you.
Also, would it solve my problem if I "downgraded" to Apple TV's first generation?
It looks like there are more outlet options on that one ...
Yes, you could connect a gen1 ATV, since it has component video. But from the looks of it, the old ATV will not have Netflix. So it depends on what you want. Me personally, I have a non-HDMI TV, but I want Netflix. So ATV is out. A Roku box or a Boxee box is a better deal for me than a ATV (either generation.) But neither Roki nor Boxee will work as seamlessly with iTunes, won't have Airplay, etc.
For you, if the gen1 ATV has the features you want, then fine. But realize that it may be at the end of it's life, so you may not get many future updates. (i.e.: in couple of years, gen1 ATV might not work with iTunes 12.) Only you can decide if that is acceptable or not. Ask yourself, other than it being from Apple, what features of Apple TV did you need and want?