Yep, the pci slots will absolutely run graphics cards. If they didn't they wouldn't be pci slots. I also ran graphics cards off of them. However, they run like crud compared to the 66mhz slot, since they are shared and 33mhz. You can also run standard PC graphics cards, as long as there is a mac compatible rom that you can flash onto it. Reflashed cards used to sell on ebay for real good prices.
the b&w g3 supports up to 1gb pc100 ram.