All motherboards supply 75W to a dGPU. That's all. The rest is handled by the PSU.
You need to monitor GPU frequency during gaming. THAT is what GPU performance is based off of.
My RX480 runs 1400MHz at 1150mV and draws about 130-140W in the process (IIRC, reported by GPUz). Or I can crank the voltage and get much higher wattage at 1400MHz and performance is the same.
Minecraft doesn't require a RX580 anyway, so there's no reason it should be any/much better than a GTX1050Ti. You're probably getting multiple hundreds of FPS on your (assumedly) 60Hz monitor, correct? Minecraft is so graphically simple, that you're almost always CPU-limited. A simple test here is to monitor CPU vs GPU usage (%). Most likely your CPU is at 100% and your GPU isn't anywhere close.
TL,DR - play more graphically demanding games.