I wanna buy a new laptop with Ryzen 5 3500U processor. I will be using KDE Neon . From what I have read, Linux has some issues with Ryzen 5 professors. Anyone has used KDE Neon on these, how is the experience ?

How specific were those issues?
I am using a Ryzen processor, no problems with the hardware, but with quite a different setup: Ryzen series 2 instead of series 3, desktop instead of laptop and OpenSUSE instead of KDE Neon.
So, if what you read referred to issues with the most recent drivers or issues with power management my answer is irrelevant. Otherwise I don't think you should be too much alarmed.