Replacing a Switching Power Supply for an AC-DC Adapter
I think you better keep using the 20A supply that works well. Pulse currents from extruders and stepper motors can be stressful to supplies loaded to the max.

So for reliability and performance, it is better to use a supply rated for 25% more than you need and consider , a longer heavy guage cable if you prefer to remvoe the supply from the fixture but then put an ultralow ESR 16V Cap near the boards DC input to handle the pulse edge's high current.