Your problem with not knowing what you have is an issue that has driven me crazy for years. There is NO WAY to identify cultivars accurately from photographs. Especially with popular species where hundreds of cultivars have been made an named.
The solution? No matter how cheap - do not purchase plants without proper labels. You will never be able to "Figure it out Later" with any accuracy.
Second, always label your plants, and keep labels fresh. I write with pencil on plastic tags, as the pencil will fade over time, but it seldom disappears entirely. Regularly replace old labels with new labels. A plastic tag is good for maybe 5 years. NEVER use magic marker, as magic markers have ink that tends to fade completely and seemingly all at once. One minute you can read the label fine, next year you notice the label is as blank as it was when new. No clue to what was written. At least with pencil, the pressure required leaves a scratch in the plastic that you might be able to read in the right light.
So protect your labels. Make fresh labels every few years to make sure you do not loose the provenance or pedigree of your trees. You go through effort to keep your AKA or AKC papers for your pedigree pooch, you need to do the same for your trees if you want to retain the "value add on" of the provenance of your trees.
In bonsai pedigree is not important, it is only the appearance of the final tree on the bench in the show. However, some cultivars are superior to others in their growing traits. Chaenomeles 'Chojubai' is a cultivar of flowering quince that at age over 25 years begins to develop a corky bark. This bark does not show on a young 'Chojubai'. THere are several cultivars of Chaenomeles that have similar leaves and flowers to 'Chojubai', for example 'Hime' looks nearly identical to a young 'Chojubai'. But 'Hime' will never develop the thick corky bark, and if you buy a young Chaenomeles, it will take 25 years or more to figure out if it is a cutting of 'Chojubai' or 'Hime'. People pay extra to get 'Chojubai', where I have never seen 'Hime' cost more than $25, even for moderately mature plants.
So in terms of sales, and or hybridizing pedigree counts.
In terms of appearance on your own bench. It really don't matter what the cultivar is.
It is disreputable to have a no name cultivar, make a guess at its identity, and then sell it to someone without being clear that the provenance, the pedigree, is bogus. So once the label is lost, there is no going back and ''re-creating'' a cultivar name. It simply becomes labelled as the generic form of its species. Guessed at names should never be perpetuated through propagation. If I propagate or sell a "lost tag" maple, or orchid or any other plant. It gets sold as "lost tag" it does not get sold as what ever guess I make.