Q
When I paste elements, is there a way to select those elements?

A
Complete the paste. Undo (Cmd+Z). Redo (Cmd+Shift+Z).

Q
Working in section, is there a way to reveal selected elements in plan?

A
Yes.

Q
How can I tell what elements were affected by a marquee stretch?

A
Undo, redo. The affected elements are selected. Current story only, natch.

When an editing action is undone, the edited element will typically be selected. Comes in handy.