Speed - highest speed always acts first?

His Biggs gets the same Wedge bonus (presumably, because there is absolutely no reason to run Biggs without Wedge), so will go first (unless you use Lando/AA as leader for an extra speed boost). If his Wiggs combo pulls STHan, then his STHan goes before your Biggs too, which will boost the rest of his team, and... gg. There is a 1/3 chance of pulling STHan, so that shouldn't happen every time. In roughly 2/3 of the fights, he should pull the other members of his team, which generally means the order is his Biggs -> your Biggs -> whatever comes next.