As far as I know, there is no collection that maps all of them and their traits. This is mainly because they seem to have many overlapping traits that are hard to distinguish.
I can tell phoenicea var turbinata from phoenicea var phoenicea from their foliar habits because I studied them in the wild, but the literature does it by watching the ripeness of the berries. One of the two has ripe berries in summer, the other one in fall. The rest of the descriptions overlap so much, that you can't tell a difference if you'd read that list.
Google scholar can provide you with phenotypical data on most populations, if you're up for digging through research papers and making your own document based on black and white pictures.
The american conifer society has a lot of data, but that's limited to broad descriptions about growth habits, not particularly foliage types.
I think that it might be easier to grasp the concepts in a broader sense. There are roughly a couple of baselines:
1a. Needle type junipers with large needles and coarse growth (Communis, Tosho?)
1b. Needle type junipers with small needles and compact growth (Procumbens nana, squamata, forever-juvenile cultivars like chinensis stricta)
2a. Scale junipers with compact tufts of foliage (chinensis varieties like shimpaku; itoigawa, kishu, blaauw, some types of sabina, some types of phoenicea, some types of RMJ)
2b. Scale junipers with coarse tufts of foliage (chinensis varieties, sabina varieties, media/pfizer, RMJ, pingii, phoenicean, procumbens, and a tonne more)
As you can see from this list already, procumbens has both needled cultivars as well as scale foliage phenotypes. Sabina can be very coarse but also pretty compact, this depends on the original location.
We have natural stands of communis around here, some turn purple in the winter, others stay crispy green. Those are different phenotypes of the same origin. Sabina var. 'no tam blight' looks way different than sabina var. sabina or sabina x chinensis, or sabina x chinensis var Old Gold. The RMJ skyrocket grows different than regular RMJ. Even within cultivars, there are differences; the procumbens nana in the US do produce scale foliage, the ones in Europe rarely do. They might originate from different areas of Japan, or they might actually come from the same stock originally. One could be a hybrid, or a natural variation. There's no telling without genetic data, since historical records are limited to breeders, and breeders usually weren't that good at keeping track of what they did. Especially with junipers that can take a looooong time to successfully hybridize and stabilize.
In summary, if you want to map all phenotypes of all families of the juniper species, you'll be busy for a lifetime. It's more realistic to stick with the four main types there are, and make a mental note that these can both overlap and be very different based on all sorts of conditions. A chinensis in the shade will produce coarser foliage, open tufts and will overall look different (less compact) than one grown in full sun.
I'm sure that answer doesn't please you. I ran into the same wall a couple years ago. I made peace with the fact that I can only really see the difference in types when I grow them myself. So I started buying seeds and plants.