+1 on endlers breeding like crazy, stick to the males
Your water is a little soft for endlers to be honest, as they prefer a gH of at least 15. I kept endlers until recently in pretty much the exact same parameters (pH 7, gH 5, kH2) and although they bred and seemed to be doing fairly well, they're absolutely thriving now that they've been moved to a hard water area. Similarly aged stock from the same parents that was relocated there earlier in their life has aged less quickly and seems more robust than the ones that stayed in my softer water too. That said, they'll probably be fine in your water, but not thrive, so it's really down to personal choice.
On the other hand, CPDs are very well suited to your water! I keep these currently and although lost a lot of the original stock to an unknown parasite/disease, the survivors and their fry are beautiful fish with really interesting behaviours, and would look lovely in a heavily planted tank. Make sure to see the fish before buying them and ask where they were sourced from if possible. Apparently they're often a mix of wild and farm-raised stock, which can lead to parasites and diseases from untreated wild fish being introduced to farm-raised fish with poor immune systems.
I'd recommend 5 male endlers (if you do decide to go with them) and 6-8 CPDs to begin with. I'd probably add a few more CPDs down the road once the fish had matured enough to be sexed - males will spar so it's good to have more females than males. Just as an aside, CPDs will eat some newborn endler fry, but can't stay on top of a whole population, so a 10 gallon would get overrun very quickly if there's a mix of male/female endlers.
Oh and as @KayakJimW
said earlier, get some cherry shrimp too!