PowerPlay estimation and asynchronous faster-than-clock signal: no clock domain found

I think your design is too small for too much concern on logic accurate transition rate as most of power would be static (as opposed to that of switching).

If you indeed want proper rate you need to look at your simulation for sometime and estimate toggle rate per signal. But it is overkill and I suggest using default of 12.5% for io and all signals.

Try then increase it and you will see the difference to be small anyway