Can I play Showstopper while all my units are buffed and could I still move a unit?
Yes, you can play Showstopper even if all your units in your base are already buffed.
According to Rule 426.1.c and the mechanics of the card:
- Showstopper's ability is: "Buff a friendly unit in your base, then move it to a battlefield. (If it doesn't have a buff, it gets a +1 might buff.)"
- Rule 426.1.c states: "Units with Buff Counters can still be chosen for actions that Buff units, but will not be Buffed as part of the execution."
- Per RiftJudge FAQ #3683, the fact that a unit is already buffed does not prevent you from playing the card; the buff will simply not be applied again, and all other effects of the card (the move) will still resolve.
Summary of resolution:
- You play Showstopper (targeting a unit in your base).
- The card attempts to buff the target, but since it is already buffed, the buffing action does nothing.
- The card continues to its next instruction: moving that unit to a battlefield.
This interpretation is supported by Rule 426.1.c regarding buffing already-buffed units and the clarification in FAQ #3683 regarding Showstopper specifically.