My nvidia 3gb cards mine ETH just fine and will continue to do so for about another 12 months (using them in secondary slots in Ubuntu which doesn't allocate ram to other purposes).

For amd cards there was once an issue but driver updates fixed it. You need to install latest drivers and turn them too compute mode. If you do that the ETH rate is comparable to alt coins. But the driver is not available for really old cards or appears. I have an R9 390 that mines 29.3 in ETH and 29.5 in expanse, for RX series there is typically no noticeable difference.