Draven, Vanquisher

This card is now banned.

Q. Do you get to see if your opponent uses a Fury power to give their <Draven Vanquisher> +2 Might before you decide to use <Reaver's Row>?

No. You place the trigger from Draven on chain, then the trigger from Reaver's Row. You resolve Reaver's Row - deciding to return your unit and returning it to base, then your opponent decides if they want to pay the power or not.

442.1.b.1: The attacking player, who has Focus, places Triggered Abilities on the Chain first, following by all non-Defender players in Turn Order, followed by the Defending Player.

352.10.c.1: If a spell or ability requires one or more players to choose objects, players, or zones that are not targets, those choices are made on resolution.

This includes costs within instructions, identified by phrases like "[do X] to [do Y]". The cost within that instructions is "[do X]".

Read also this FAQ about triggers and templates.