Assuming the spores you were able to make are the right kind (reads like they are from the description of aroma and look) you product will be similar to something made from vision or gem or AK. Its fresh, so you get to see what its like when new, vs something sitting in the cooler for a few months/years.
As for flavor contribution? Absolutely most definitely koji will effect your sake's flavor. How you grow your koji, under what moisture/oxygen/temp conditions all determine not only flavor but enzymatic activity - which also controls flavor.
Your koji being tangy might be due to some lactobacillus or other organisms in with your koji. Is your koji white/offwhite?
If its green, do not use it.
Do you have enough for 2 batches of sake? Make one with yours the other with cold mountain and compare. Sounds like your koji is good to go?