The best are ones that completely change the screen frequently, which of course newer games are better about. However, if the game displayed changes frequently - I prefer a minute but two is okay I guess - I shouldn't think there to be a problem.
On the second thing, MAWS, likely.
On the third, if you're going to display native for each game, then of course the resolution for each one will have to be set. 15khz is 15khz - thought it's conceivable the AVGA drivers have some stock differences in brightness, hue, etc than other standard cards.