could i scratch with this?You can scratch with any turntable provided you can keep the resistance at a level you don’t have to “push” the record back on beat.
will it ruin the turntable (motor, or whatever)?That’s what slip mats are for. Should keep almost all resistance off the motor.
What type of needle is preferred? “preferred” is subjective. I prefer Shure M44-7’s.
what type of vinyl is preferred (thick/thin not sure what the technical terms are)?I have no idea how to answer this except to say the type of vinyl with beats and sounds you like.
You can scratch on it and even mix (though the pitch control is not going to be east to fine tune as it’s just a little dial). And definitely get the slipmat and practice manipulating the record without disturbing the movement of the platter – as lotus said, keep the resistance off the motor itself, the slipmat will let the record float but it’s always tempting to push down on top of the platter so be careful. I suspect the motor on the D20 is not able to take the kind of abuse that the 1200 can take.
You’re going to want to save up for a turntable with better pitch control, better tonearm and a heavier mechanism, but it’s not a bad turntable at all to start with - much better than my first turntable for sure And you might take a look at the cartridge that’s installed and try to replace it with a Shure or Stanton.