@EVAL's internal precision?

How many decimal places doe @EVAL use internally?

I mean, if I use @EVAL[w+x+y+z=2], does it add four precision-2 numbers or does it use higher precision and round the result to 2 places?
Another, mostly unrelated question about @EVAL ... in a plugin, are these equivalent. Paraphrasing a little,

1. ExpandVariables(L"%@EVAL[expression]", 1)

2. ExpandVariables(expression, 1);