Endli (WHITE VOLTA, BLACK VOLTA, MILO, GUINEA, FARAHNA, NIGERIAN, ETC.) are ALL collection points. It describes where the endli was collected. NO ONE can tell for sure where an endli came from just by looking at its pattern/headshape. IN GENERAL, there will be recurring characteristics between one collection point to another (ie size of head, patterns), but again there is no way of telling unless the supplier tells you the collection point. You can have 10 endlis from the same collection point, and all 10 look different from one another.
In lower jaws there are two general COMPLEXES in bichirs, the ENDLI COMPLEX & the LAP COMPLEX. For example under the endli complex you have endlis & sp. Dabolas....etc. Whether sp. Dabola is a wild hybrid or its own species, the head looks like an endli.
Under the lap complex, you have laps & sp. Koliba & sp. Koloton...etc. Again with sp. Koliba & sp. Koloton, their headshapes are that of a lap. There is debate over whether sp. Koliba & sp. Koloton are the same species OR are just collection point variants. Either way, they belong to the lap complex.
Comparing any bichir between endli complex & lap complex are comparing apples with oranges. It comes down to personal preference. They are different species and their headshape appearance is correlated to their corresponding complexes.
Red Garnet sand IS THE BEST substrate for color & patterns in lower jaws. There is none better. You can experiment, BUT again, red garnet is the best to use. Anything else has the potential to wash out your bichirs.
Best of luck!!