No socket-7 chipset did more than 2x AGP. As long as the board does implement AGP 2.0 though (yes AGP 2.0 does allow 1x/2x-only implementations!), you got enough power supply strength to feed a current card.
You just need to watch the backward compatibility - the latest cards (e.g. ATi 9600 series) no longer are backward compatible to the 3.3V signalling required for 1x/2x modes. Still plenty on the market that is though, e.g. ATi 9200 series.
Cards that are backward compatible have two notches in their connector blade, to fit all kinds of AGP slots, no matter whether they have the 3.3V or 1.5V key tab in.
In general, you shouldn't aim too high anyway since the slow CPU will not be able to feed a fast graphics card. And I'd stay with ATi rather than NVidia, to keep the card's power draw low. Socket-7 boards and the case power supplies of the time just aren't ready for those power hungry GeForce monsters.
I'd say an ATi 9200, even if it's a fanless non-pro version, should already be more graphics speed than the K6-2 can feed, with power consumption and AGP compatibility both on the safe side.