Cacheman is a good program for helping to stabilise your system if you are having problems with 512 or more of ram when using Windows 98, 98SE or ME ( XP doesnt suffer as badly with VCache or Vmemory problems ) . Please note ..stablise.
I used to use it with my old ME system, to stop system crashes, as Vmemory was a constant problem..( ie Blue error screens etc ). But in the end I had a faulty memory card and overall Cacheman didnt really seem to do that much,..ie I didnt notice any difference in game performance, just that they didnt crash halfway through.
Although it did obviously allow you to instantly see how much memory was being used up, and try to free some up...( More helpful when opening a lot of Pictures from a digital camera )
The good thing about Cacheman is that is saves all of your registry settings before you make any changes so that should you have problems, you can revert easily back to your old set up.
As you have stated, if you want to use it, you just click on the games settings and click load, whether or not it will make a noticable diffence depends on your individual set up.
You already have fast DDR Ram, and plenty of it, if you are not experiencing crashes I wouldnt expect it to improve games that much if at all.
And you know the old saying... " If it aint broke dont fix it " !