I use temp from an external Garmin Tempe sensor and it works well for me. As for Pressure, the Tactix never uses environmental data from a phone, it has a built-in sensor to determine Station Pressure.
Humidity can be set to 50% for "most" shooting without noticing a difference. The longer the shot the more humidity becomes a factor. If I'm shooting PRS I don't worry about humidity, if I'm shooting ELR then I enter the humidity manually.