Can I adjust the corner frequency of the low-pass filter?

Moku:Lab Laser Lock filter filter configuration

Yes!

The low-pass filter corner frequency can be tuned from 1 kHz to 14 MHz.

You can also select different filter types including Butterworth, Chebyshev I & II, Elliptic, Cascaded, Bessel, Gaussian and Legendre to notch troublesome resonances.