I find rows counterproductive; they make it less obvious how full the board is, and don't help make better decisions. By all means sort each column in priority order so that people picking up a new task know which to pick up first; that's a lot less intrusive and covers the important use case.

Likewise sub-boards and meta-issues. If we're doing agile properly then each card represents a user-facing deliverable. Allowing meta-issues encourages doing the wrong thing.

Limiting work in progress I've achieved by having people assign themselves to cards, and questioning those who are on multiple cards. In the cases where we're violating our work-in-progress limit, I'd rather have the board reflect reality than not.