Yes, this is pretty much correct, yes!

one little addition:

2 and 3 can be the same.

Alby Hub comes with a default embedded LDK based lightning node - or Alby Hub can be used with an existing LND, phoenixd,..

Alby Hub exposes NWC - apps can connect using NWC to the hub (whch is also what getalby.com) does)

The Hub implements the node part either embedded or external (LND)