I use a 1TB Gold v4 most of the time and a 512GB Gold v2 as backup. I used the 512GB one extensively in the original R5. So far both cards have been reliable. I really appreciate being able to offload images and video at >2.5gbyte/s with the v4 card!
The only annoyance I encounter with the R5II and these cards is that the camera startup takes a few seconds longer. With the original R5 Canon issues firmware updates to improve this startup behavious, I hope they can do the same for this new generation of bodies.
So far no other delays or complaints!