by default are component thru hole pads in Via style in Eagle software?
Yes.

This is the default for everything, and you have to jump through hoops to have your manufacturer not plate the holes, at least for the cheap ones that I use.

Normally, if there is any copper over the drill hit, they will plate the hole, but you have to check with the individual manufacturer. Seeedstudio, which I sometimes use, has a more confusing solution, where you have to encoded it in the solder mask layer.