So here are my findings:
If I clone USB drive to ExtDrive the only way to boot ExtDrive is from USB2 port on RPi4, which is no-go for me due to speed limits (I tested all 4 ports on RPi4).
ExtDrive is only booting from USB3 port when I "dd" LE img file to ExtDrive or use netinstall followed with initial boot but that ends with corrupted FS in both cases.
So I think there is a bug for resizing partitions during initial boot after placing LE img to bigger drives.
Or, LE has limit for the size for external drives that can run LE from (worth documenting I guess).
I can share drive info later on.