Correct, all communication is local for both integrations.
I am not sure if the official is different from the HACS integration but I have had no issues with the HACS one. I think I saw somewhere that the official is based on the HACS version but not sure if that is accurate. I have not used the official integration due to the HTTP requirement.
I have 3 gateways (GW1100) with the following sensors and all have been rock solid for well over a year.
- 21 soil moisture sensors WH51 (only replaced 1 battery so far)
- 2 soil temperature sensors WN34BS
- 1 indoor air quality sensor WH45
- 1 weather station GW1102
- 3 temperature and humidity sensors WH31