When you lock the card in MSI Afterburner you override the powerlimit. The powerlimit doesn't effect the powerconsumption at all. It's basically the same thing as using --lock-clock in TBM or with nvidia-smi. All the cards are locked in MSI Afterburner.
TBMiner v1.16 support setting the powerlimit to. If you set the lock clock too high, the core will trottle. Higher coreclock more heat, more cooling needed, so you want stable clocks, stable fanspeeds.
But when you reach memory speeds of around +1500 or higher you need to push the core above 1200Mhz to reach maximum speed. I found you need atleast 1470Mhz for the GPU not to bottleneck the memory when the memory is at +2000.