You've got to stay under the engineered current limits on the provided 3.3v, including how much current is reasonable on all the wiring to your boost converter, but chances are good that mouse transceiver uses much less than the typical usb bus powered maximum current of 500 mA, and even at 75% efficiency, that's about 1 amp at 3.3v, which doesn't need thick wires or traces, or a big power supply.

The transceiver probably does use more power than a fingerprint reader, especially if the reader is idle, but likely not enough to worry about.