The Conquistadores came in the main from (or through) the already established colonies in the Caribbean and along the American coastline. Usually more-or-less middle-class types and lower gentry looking to improve their fortunes and so on (a while later the equivalent method in southern England and the French coast was piracy and privateering). Former soldiers were actually pretty rare, although I wouldn't be all that suprised if many of the men had had some sort of militia training and education in swordsmanship and suchlike was pretty widespread in the societies of the time.

There were also surprisingly many enterprising African slaves in their ranks - capable folks whom their owners had let off to earn the money to pay for their freedom as a sort of investement, and partly to keep such clever fellows from plotting trouble in bondage.

Opportunistic native aristocrats apparently turn up rather often in surveys of post-Conquest landowners too, although obviously these folks wouldn't have fought in the ranks as conquistadors but instead led native allies.

As far as German ritter's with pistols though, I can accept that if it's late enough since IIRC that was a common if less than stellar cavalry tactic in the late Renaissance up to around the 30 Years War to ride into pistol range, fire on the enemy, and wheel about to ride back and reload (though the name of the maneuver escapes me, and I'm not sure of exact dates, especially since I can't remember the name to look it up, grr).
Called caracole, Italian for "snail". Really more of an anti-pikeman tactic as well as the cavalry equivalent of the infantry countermarch (ie. rotating musketeer ranks), but conditionally useful against cavalry too. Already known in the Spanish-Dutch wars of the 1500s, where the German mercenary Reiters (forerunners of the heavy cuirassieurs of the Thirty Years' War period) also saw action. A parallel technique used already in the French religious civil wars of the late 1500s was known as pistolade, and consisted of discharging the pistols against the enemy at short range and following up with the sword; the Swedes reintroduced this when they entered the Thirty Years' War and it soon became the norm for cavalry warfare.

Nothing to do with the Conquistadors though. Those sorts of tactics practically required wheellock pistols (flintlocks only started turning up around the mid-1600s), which were not only very expensive but also mechanically unreliable and delicate. No way they could have survived the American campaign conditions, especially as repairs in practice required some fairly skilled craftsmen.