This is still WIP, but will definitely get an option before it’s enabled by default. I too much prefer apps just following my configured placement policy.

No, nothing has been changed. You can opt in to default to copy because a lot of users asked for it. The default behavior is the exact same it’s been ~forever.

Then just change the rule to not include the debug console…

Yes, it’s a bug that was fixed in 6.3.2

Screen mirroring is kinda shitty rn, this might get fixed with future changes for Plasma 6.4 (which make it less shitty in general). It’s probably worth fixing this as a separate thing for 6.3 though, so please make a bug report about this for KWin at bugs.kde.org