As pointed out above, an Ultra-6 has its small cog flush faced. As opposed to the standard 6 which has a 'lip'.
The 4-prong Winner Pro was released after the 2-prong New Winner.
You are correct. The New Winner and Winner/Winner Pro are simply freewheel body styles. Defying common logic, New Winner actually preceded Winner/Winner Pro. Both could be configured as regular 5 or 6 speeds and ultra (narrow) 6 or 7 speeds. Winner/Winner Pro accepted all the cogs/spacers used on New Winner, but also splined cogs in the middle stage, which made assembly/disassembly much easier. The difference between Winner and Winner pro was in the quality of the bearing races, which were machined on the Winner Pro, and were noticeably smoother. They could be distinguished by a silver outer lockring on the Winner and a gold one on the Winner Pro.