I've only been to Kenya but @PeteJChurchill's photos seem to have loads more vegetation. I remember wide grasslands so not much in the way. Random example (from ~2004, shot on film with a 200mm lens IIRC).
I’m also team X-T3 and have all-the-lenses™️. I agree that the 100-400 is the best choice as the 150-600 is limited to f8 at full range and doesn’t focus well in anything other than bright conditions.
Plus you can buy a x1.4 tele converter for the 100-400 for a bit of extra reach if needed.
I've only been to Kenya but @PeteJChurchill's photos seem to have loads more vegetation. I remember wide grasslands so not much in the way. Random example (from ~2004, shot on film with a 200mm lens IIRC).