Ich-X is usually my go to treatment, as they are not responding to that the next thing I would try is salt. But be careful as it will kill your live plants. Plants and salt do not mix. In my experience the combo of salt and ich-x usually knocks it away in a couple of day.
As how it is compared to copper I can't say, I avoid copper because it is harsher med and also not invertebrate safe.
I have found some rasboras to be sensitive to velvet outbreaks, particularly when there are shifts in temperature.