The best setup I've used so far is a standard whiteboard coupled with a projector (ideally with a second board to the side). It needs very regular cleaning to prevent a blurry display, but being able to write normally (being able to see what you're writing with zero lag) is a huge benefit.

If you really need at-board interactivity (as opposed to keyboard+mouse at the PC, or wirelessly, or casting from a tablet, or...) then Epson do a projector with an IR "pen" that works with any old whiteboard.

The company never cared about end-user experience until it was too late. They raked in the money when education budgets were high and every classroom could afford a SMART board and sat on their hands after they IPO'd.

The people there are fantastic, but it just wasn't possible to steer the ship fast enough to kill the old culture.

I don't know your workflow or requirements but it might suite. I'm not associated with them.