What is the most effective strategy for playing early position and how does it vary depending on the type of game (cash vs. tournaments)?
This is a very general so I assume you are at beginner level. I would recommend you get the free version of GTO Wizard and look at preflop ranges both Cash and MTT and you will see what the basic strategy in EP is.
Some players will say "play tight" but that does not define strategies well enough for you to progress effectively
for example in Cash 100bb EP open we would call a 3 bet vs BTN with 65s but not QJs would you consider that strategy as "playing tight"? We are also folding A9s 100% KQoff 100% AQoff folds 60% AJoff100% -Would a tight player fold these
hands and if yes are they then folding too often if they do not call with suited connectors at some frequency?
So if you incorrectly apply "playing tight" you will lose a lot of money calling with dominated hands or over folding.