Hi @reinhard-schmid! The Wacom tablet should work fine, particularly in Chrome. Many of our artists draw that way. I'll ask our tech guys about Firefox. I remember there is an adjustment to a setting you need but I don't remember which one right now. :(
As for pasting, what makes us unique is that we encourage people to get to know each other freshly and spontaneously by drawing. You can always share a link to your previous work in the comments or the chat. We may incorporate uploads in the future... Thanks for trying it out!