Hypothetically if the House size were increased, would make gerrymandering better or worse?

[Del Tachi]

Yes, you are correct that the more districts a geography contains the more proportional the map becomes.  A map of single-voter districts is theoretically the same as full PR.

More seats also mean more required minority-access and minority-opportunity districts, which is a net benefit.  For example, MS gaining a 5th seat due to reallocation probably triggers a second VRA district.