In any club this large, there are identifiable tensions. Before you visit an SCA event, it might help to know some of the major factions. These divisions are rarely serious enough to spoil the fun, but you might as well be aware of them to avoid treading on somebody's pet peeve.
Within the SCA, you will find a few people who are serious historical re-enactors. They place a great premium on authenticity. You will also find a few science fiction and fantasy fans, who wear pointy ears and pretend to be elves. Most folks are in between, being authentic when it suits their taste and budget, but not being overly strict about it.
Most SCA members are attached to their local chapter, and as part of the game may make a big show of fealty and devotion to the current king and queen. However, some are more like members at large, and may belong to non-regional sub-groups like the Mongol Dark Horde.
There are SCA members who love pageantry. When club members get awards for service or achievement, the king holds a great court, with heralds, and scrolls, and people shouting "Huzzah!" and "Vivat!" Other members would rather watch paint dry, and complain that court always takes too long and makes people late for dinner.
Among the fighters, there are those who are serious about winning awards and tournaments. Others just love to armor up and whack their buddies with big clubs or shoot them with blunted crossbows. The former is most at home on the tournament field, testing their mettle one on one. The latter loves big battles where hundreds of fighters storm or defend a castle. Most fighters do both, but a few will specialize in one or the other.