How To Tell If Opponents Are Tactical Or Positional - Without Accessing Games

OK, that is a big claim, but I believe how players arrange their knights is a good clue as to their chess style.
If the knights are pointed face on at you, the opponent is mainly tactical; if they are placed side-on, positional play will dominate.
The very occasional opponent who places knights at a 45-degree angle is among that rare breed -  a balanced chess player (balanced chess-wise, that is; I make no claims as to anything else).
Similarly, an opponent who minutely adjusts each piece before the start of a game could well be a perfectionist who will end up in time trouble.
Naturally, I accept that these hypotheses need further testing …