board is smaller and interface is laggy

Not sure how your board got out of whack. Go to lichess.org/account/preferences/display#displayBoardResizeHandle and make sure "Show board resize handle" is "Always" or "Only on initial position". Then go to lichess.org/analysis and there should be a little handle in the bottom right corner of the board you can drag to resize it.

@schlawg said in #2:
> Not sure how your board got out of whack. Go to lichess.org/account/preferences/display#displayBoardResizeHandle and make sure "Show board resize handle" is "Always" or "Only on initial position". Then go to lichess.org/analysis and there should be a little handle in the bottom right corner of the board you can drag to resize it.

or:

We didn't change the board. The resize handle has been there for a long time.

You're in control of board size. If you've dragged your board size to 100%, that's as big as it will go. We haven't changed the max board size*.

* much

Regarding the interface being laggy, mind providing your platform details? And what background theme are you using?

You can use this to lookup and send us your browser info: lichess.org/#debug