you will need to ensure that the excitation spectra of both the indicator (voltage or calcium) and the opsin are sufficiently separate so that you don't have any crosstalk, i.e. the imaging wavelength exciting the opsin.
Our lab found a solution using Chronos for the opsin and CaSiR-1 for the calcium indicator
Article All-Optical Crosstalk-Free Manipulation and Readout of Chron...