Just my thoughts as a long-time pro engineer:
1-fixing this is not very likely and I'm not convinced its an issue.
2-its very common for different brands of converter to have different amounts of latency.
3-its something to be aware of so you don't route certain combinations of inputs thru different converters, such as your left and right overhead mics, or any 2 inputs from a stereo source.
4-with the difference you are talking about, if you adhere to my #3, you will likely never hear any issue. I never did with my drum mics going thru a Midas XL48 coming in via ADAT and my overheads coming in from a Focusrite ISA-428 on analog inputs of an HD IO(its about the same as moving the overhead mics a few inches closer or further)
5-(again, my opinion); I believe you are over-thinking it