sending differential signals off board, what kind of connector do I use?
I would use the Samtec QTH-DP and you can definitely send single ended signals through it. LVDS is defined as a 100 ohm differential signal, so this is a suitable connector.

You do not say just what speed (or more importantly, the edge rate) of your differential (or single ended) signals are, but if you use this type of connector you are covered at least for the LVDS pairs.

The typical single ended impedance is about 60 ohms through such a connector (this may well be in the report for the connector - Samtec is extremely good in providing such data).

I would note that Samtec offers complete cable assemblies for such board to board applications which can come in useful.