Different or the same alpha should make no difference. If you use noconflict and two of your processes send different data at the same time (e.g. uid 0x01 name=“bob”, uid 0x01 name=“dave” then it is not deterministic which name 0x01 will get.
If you have already processed the data in RDFs, can you send e.g. 1000 RDFs in a single transaction? That is the most effective way to speed up your inserts.
RE python, I am just a community member and not from Dgraph, so perhaps they can comment as i use Go, not python. To me your example looks correct.