Just remembered watching a custom exhaust build on one of the hotrod shows I watch, 5-6 of them, always one on at any given time.
They were doing a X-pipe, which has mostly gotten preference now over the older favorite, the H-pipe. They sliced off one side each of 2 only slightly bent straight pipes, sliced off the outer skin of the bends, welded the openings together, then continued the separate tubes.
The X-pipe idea isn't of crossing the pipe directions, but rather just letting them be freely together for a second. Helps with scavenging. Maybe some kind of angled slices like that could begin the 2-to-1 transition you're debating.