Linear vs Circular Polarised

Hi Everyone,
Are there any instances where a Circular Polarised antenna would be more appropriate than Linear for OpenHD?

I’m currently building a fixed wing that needs to get in behind trees, into valleys and canyons, with about 2-4km range. Outright distance isn’t my objective here.

From what I’ve read on this forum is that Linear seems to be King, yet I see DJI have gone Circular Polarised on their HD FPV goggle system which gets a claimed 4km.

An example of CP antenna that I am considering is the VAS Madmushroom V2 CP antenna which pretty much covers the entire 5Ghz range and is suggested for HD systems.

Any issues using both Linear & CP considering most RTL8812AU wifi boards support dual antennas (on both Air & Ground sides)?

I’d really appreciate any thoughts or recommendations.