The only etiquette around shots that I know of are:
1) In mixed-doubles (or co-ed singles), a man should not rifle 100mph forehands trying to take out the opposing female if she's at net.
2) In singles, if the guy is up at net and you get a floater/sitter which allows you to crush an easy putaway... you don't just peg the guy at net. You pass (or lob) the guy if you are able to.
3) If a loose ball wanders onto the court, you call a let. If you choose not to call a let, you don't hit a shot to the vicinity of the loose ball... and risk your opponent's health.
Other than those things, hit whatever shot gives you success. If your opponent can't run to get a dropper... or can't get into position to take a high ball... then do that all day long.
2014 Head Youtek Graphene Speed Pro
VS Gut Mains 16g @ 56lbs / RPM Blast Crosses 17g @ 54lbs