Yes, the PDC use the Unicorn Eclipse Pro dart board, it has razor thin wires so it increases the size of doubles and trebles, but only marginally. The BDO use the Winmau Blade III, it has thicker...
23.
Since you can score any of the numbers 1 through 20, plus you can score in the double (outer) ring, or the triple (inner) ring of any of those numbers. 1 through 20 is obvious, 21 can be scored...