Can a controller control two amps at once?

Yes. The foot switches and leg mount controller can control more than one amplifier at once by either using a Cat 5 splitter or on equipped controllers by using two outputs at once. Quilter amplifiers that can be controlled via external controller typically have one Cat 5 jack for controlling internal circuitry. 

Please note the Overdrive 200 does not have a Cat 5 jack. But two can be controlled via split 1/4" trs cable. (Common headphone splitter would work just fine.)

The 6 position controllers have two Cat 5 jacks and can control two amplifiers. 

The 2 position (Channel and reverb) and 2 position select-able. only have one and would need a Cat 5 splitter.