Using a fast USB drive, there is, in my experience, not very much difference between resident programs and programs loaded from the compressed image. This has to do with the development of a lot of factors, making the USB work better and better with time. My personal opinion is that CD/DVD+ "toram" option is simply the wrong way to go. But with 64-bits kernel and 8GB RAM, loading the whole image to ram should work - taking some time, though...
Trying to load parts of the compressed image isn't worthwhile, I think. I strongly suggest people comtemplating more "manual" RAM management - IMHO the combined work of Knoppix and the Linux kernel works very well in this respect try fast USB devices first, USB3 makes a lot of difference too.