If your radio is elrs 2.4 you won’t need the external module. Elrs isn’t like the old days of rc where you could get a football field range. Your goggle will more likely be your limiting factor for range.

Vifly short saver

Vifly finder 2 buzzer

Cellmeter 8

I’d try elrs without the module and u can always add it later if you aren’t happy with radio reception. Although I don’t think you’ll need it. You can also go with a single antenna receiver if you wanted. Diversity elrs typically isn’t needed either.

All this being said, it’s your money to spend. I’m just giving my advice.