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I use one and don't have any issues or lag. The only issue I have is the adapter sticks out a lot which keeps me from putting my PC all the way against the wall haha
Depends on the GPU. Some cards(r9 290 for example) dont have dvi-i ports only dvi-d. A simple dvi to vga adapter will not work in a dvi-d port, they require an active dvi-d to vga converter.