The effect of CPU governors when Min and Max frequencies are the same
This depends on the kernel, CPU and governor of your device.
If you lock your minimum and maximum frequencies to the same value, only hot plugging really affects your CPU:


On multi core CPUs: Yes, the governor has an effect, because different hot plugging behaviors may pause CPU cores at different situations (be faster with it or wait longer).
On single core CPUs: Unless deep sleep is not prevented, no, because the CPU can't access any other state.


So in your situation: Yes, it will have an effect as long as hot plugging is supported by your kernel and CPU.