Ideal speed is a moving target. That’s why it’s suggested that an IVT is best for blowing snow. I use a John Deere 8320 with power shift on mine. It works ok, but I basically have three speed options as 4R is way too fast. I had been using a 4440 with Syncro-range. That gets old pretty quick shifting from forward to reverse. But I used it for many years. The swivel seat helps a lot on the neck too. Rear window wiper is a big help.
Speed depends on how much snow you have to force through one, and how wet it is.