Bush has very little intellect, so I'd be hard pressed to see him as a key decision maker in the administration, unless of course the decisions are arrived at without thinking. I think its safe to say that Bush's economic policy is arrived upon in conjunction with the needs of his constituents, his public message and religious slant influenced by his political team based on appealing to voters, while his foreign policy is handed down to him from the neoconservative hawks, aka. Wolfowitz, Pearl, Feith, Cheney, so on so forth. I don't see him as a particularly tactful and passionate debater, which is basically what you need to be if you are going to go into the presidency with a staff of veterans and leave your own mark. It might not be far fetched to say that Bush and Cheney are co-presidents of sorts. Cheney certainly takes a far more active position within the administration than is customary for vice-presidents, and many of the administrations policy decisions are more in line with Cheney's far right ideology than Bush's center-right campaign stance from 2000.
