Did you download the correct fu24_a9 from the google drive link? That version actually has the camera lenses labeled as 5x, 2x, main, and 0.6x. I had the same problem on some of the other fu24 ports but the drive link corrects it.On my Mi Note 10, aux3 has the same field of view as the main cam. Also, it is in 4/3 aspect ratio regardless of the xml loaded.
I am giving up on finding a gcam for regular use. I have discovered open cam and find it the most functional cam app for my phone. It is satisfactory and reliable for daily use, but is weak in low light. So I am also keeping miniflex for ns.