Digitally selectable filter
It would be better to have 560 ohms to ground, and use only one transistor, switching a value of 3k (should be 2.9k) to ground. That way most of the current flows in a real resistor, which minimises any distortion coming from the transistor.

2N7002 looks fine, any MOSFET should do as long as the gate is driven properly.

Unexpectedly, bipolar transistors can work moderately well in this mode. If there's plenty of base current, then the collector can both sink current to the emitter, and source current from the base. A low VCEsat type is needed for this to work well, Zetec seem to make transistors that are good in this regard. There will be more distortion with a bipolar than a FET, using a single transistor as I've outlined above is especially important for minimising it.