Setup whatever mics you have available (well matched or not) as a pair placed at the front of the stage or hung above the stage. Its a small club and you'll need that to get a good representation of the sources which are not well represented or even present at all in the PA output from the soundboard. That includes pretty much anything which is especially loud onstage- guitar amps especially, possibly drums and cymbals (not kick drum), maybe bass, etc.
A mix of the mic pair with the soundboard feed should be able to get all on stage sources represented evenly and clearly, including vocals. That balance and clarity is more important than nice-to-have additional stuff such as mic'd room-sound and audience-reaction. You'll probably get plenty of those things in your mic source anyway, probably with an appropriate balance if the mics are located at the front of or above the stage.
For the mis-matched mic pair, I suggest either a wide near-spaced stereo mic configuration or a parallel A-B spaced stereo microphone configuration - spaced say 3' to 6' apart. In all likelihood everything routed through the soundboard will be mixed to mono in the PA, and all that stuff will image dead center in your direct soundboard recording, so err towards over-wide rather than over-narrow in the microphone configuration to generate sufficient stereo width and interest. A parallel A-B setup is likely to help mitigate the mic-mismatch more than a near-spaced or coincident stereo configuration, and works well in combination with the mono soundboard. If placing them overhead, don't go too low over the drum kit, the idea is to get a good representation of all the sources as heard on stage rather than overly highlighting the cymbals and drums.