In answer to your questions

Paul Brotherton gives his advice on overtaking
From Stephen Iles: Which is the better side to overtake on - windward and risk a luffing match and keep clear or leeward and get dirty air? It all depends on the tactical situation. If for instance, the leg is long and quite free, then there's a good possibility of being able to pass boats to leeward. However, on short, tight reach legs, going low can be fatal, as once you're caught below a line of windward boats - there is no wind. One crucial point to remember when passing boats to leeward; don't simply point the boat low and expect the work to be done for you. Pick your moment, be that surfing on a wave or on the face of a gust. Top tips. If there is any tide or current, know exactly if it's going to take you high or low on each leg of the course. Try and quantify this in boat lengths per minute, i.e if you are off on a beam reach in less than six knots on a standard Olympic outer loop, you may well be on that reach leg for three to four minutes. This would be the primary focus for your decision about whether to go high or low.