Why does it turn on and off again?

Thermostat function, when the wax is finished melting, it will cool down for a few minutes and then start heating again. Ensure that the wax can be controlled at the temperature you set as much as possible, the wax is not heated all the time.

How much wax can the large single wax pot hold?

Probably each pot can hold 500ml - 600ml melted wax. And if you purchase double wax warmer, totally two pots can hold 1000ml -1200ml melted wax.

Can it work in europe on 220v?

No. At present, the products we sell in the U.S. are all 110v.

What type of wax beads are best with this warmer?

It suit for hard bean and soft bean

Can we use one side for hard wax and one side for soft?

Of course.