Smoke detectors & backup generators
California also requires battery backup for hardwired detectors.  So you could separate that circuit from the generator safely.

Most consumer level power generators do not produce the same quality of power as the power company.  Total harmonic distortion (THD) may be much higher.  Generac is a good company, but they don't specify a THD on the data sheet for  their 11/10kW Guardian Series generators.

I find that regular loss of power sets off hardwired detectors.  I just consider it a power failure alarm and move on.  The switchover from the power company to the backup generator will never be 100% smooth at this price level.