Daughterboards are accessed over the MIDI port, like an MT-32, except that they're on a card attached to your sound card. The waveblaster (daughterboard) is just a power connector and MIDI connector (out) and stereo line level (in). To set them up in a game you just set it to MPU-401 MIDI or SCC-1 mode.
An AWE doesn't have an actual hardware MIDI port, so untill the drivers are loaded it does nothing because MIDI cannot be sent to the daughterboard.
As for which to buy, either an SCD-15 (basicly an SCC-1 on a card) or DB50XG (basicly an MU-50 on a card)
The DB50XG, while it acts and sounds like an MU-50, actually used the same chipset as the QS300, and because of this it had a hidden edit mode that Yamaha did it's best to hide because they didn't want budget minded musicians buying a cheap daughtercard rather than an expensive keyboard. What this means is that you can get access to the low level voice parameters and make your own sounds using the ROM samples. (it's still used by musicians on a budget because of this)