It depends a lot on the use case, if your use case is 10’s of thousands of times slower than regular C# I can’t really provide any reasonable estimate since that’s far out of the ordinary from Udon’s current performance characteristics. I’d still expect it to run faster under Udon 2 in your case, but I couldn’t say how much.
In general it can be a few times faster or more. I’m sure you could find some case where you’re able to make it perform a bit slower due to needing to marshal a ton of data or something too frequently though.