I am also starting on my X4 batch 6. These forum links have been the most help so far:
[OpenPPG 22 v3.1 Build Video] (OpenPPG 22 v3.1 Build Video (part 1) - YouTube)
[Greg’s Batch 4 build] (Greg's Batch 4 build, maintenance, repairs, upgrades)
And especially the link to another builder’s photos in the latter. There seem to have been running design changes to the kits and material mismatch / shortages (mainly fasteners) have happened.
I’m just starting on the wiring.