There are even variances within the 'games' -- I've seen some played straight up, some where walks are not allowed, some where each side plays to six or nine outs to save time.
The games, although the more comfortable setting for many players, can be a problem at some showcases. You can be an outstanding third baseman, say...but if nobody hits it to you, nobody there will know. You may come up repeatedly against poor pitchers, and spend your 3 or 4 ABs walking, or flailing at pitches out of the strike zone to try to show them what you can do.
This is why you ask about the showcases you are thinking about, so that you will go to the ones who are consistent with the level of talent they invite and whose format you find comfortable.