As a rule of thumb, if the results list shows 4 or more horses with CSI of 18 or above, it is usually a good mating. If it shows 2 or more horses with CSI above 20, it is usually an exceptional mating.
Ok, got it, didn't read the fine print, and I use that feature all the time. But G1 and the other nicking services (enicks & truenicks) aren't quite the same. G1 will give you a pedigree with the contributions of all the horses in a 5X, both male and female, sireside and damside. It's very graphic, and you can look to see if the components of the particular pedigree are meaningful to what you are looking for. It has it's drawbacks in that not all stallions are listed and you can't get at the ones that aren't just by paying more money, but you can jiggle around a bit with similarly bred stallions.
The nicking services only match sirelines. So what G1 might think is a great match with 2 horses at "above 20," enicks or true nicks might rate as a "C" if not enough graded stakes-winning matches were found for the two sirelines involved.
Since you are using all three services they are all useful in their own way. They can give you insights as to what might work. But I think looking at the individual stallion is more important, because the grades for the stallions don't take into account the individual stallion's own stats. Full brothers, one being great and the other being awful, both will produce the same "nicks" or G1 CSI.
Also, I like the "pedigree search" feature on G1 to see how certain crosses have worked historically. That feature, combined with their VGS feature, is very useful.
Also keep in mind that none of these ratings are written in stone, they are constantly changing as new stakeswinners are added into the mix. I had a cross that I was looking at a few months ago that I liked because I really liked the stallion, but the cross was a "D." Three months later it was miraculously an "A." I always assumed it was because one of the stallion's progeny hit big (it did) but his farm also was recently added to their client list, so it did give me pause.
I'd also take a look at the conduit mare profiles for a prospective foal, another useful tool in planning a mating.
Good luck!