What is in your opinion the most efficient way of playing in poker? Or what is your personal style, And why?
I'd categorize it in 4:
1) "GTO"
2) tight/aggressive
3) exploitative
4) Nit
There are more than just these 4 general categories, but this is a decent starting list.
I could add categories like:
5) LAG (Loose-Aggressive)
6) Maniac (Megalomaniac is the long version of this name, but this player plays much looser than a LAG and sometimes plays any two cards xD)
7) "Slider" (Specific type of Maniac which goes All-In every hand or All-In at an extremely high frequency - the name "Slider" is something Phil Hellmuth invented [I think it was in his poker book, Play Poker Like The Pros] to describe these players who "slide" all of their chips into the middle too often.)
8) Reg or "Regular" at the tables which is usually a decent player, but not always. A Reg could be any of the other categories of player, but usually a TAG (Tight-Aggressive) or a LAG.
9) "Small Ball" advanced style popularized by Daniel Negreanu in his book "Power Holdem." This style is highly read-dependent and outplaying players postflop and open-raising small sizing to steal the blinds. This playstyle also plays a lot of "smaller" cards like suited connectors (98s), one gappers (75o), or cards with postflop potential (A5s). The utopian scenario with Small Ball is to steal the blinds often (so exact cards don't matter) or two hit a Flush or Straight etc. to trap hands like Top Pair by opponents overplaying them to "exploit" your wide range of hands; luckily for the Small Ball player, the trap has been sprung and sometimes players aren't able to get away from strong hands which the Small Ball player has beat

10) "Spencer's Approach: Fire Up The Game" This was also coined by Hellmuth in Play Poker Like The Pros. Many years ago in the Bicycle Club Casino (Los Angeles), a Reg named Spencer Ouren would play $80-$160-limit hold'em and open-raise EVERY hand to the maximum (for the limit game) without even looking at his cards! This sounds like a maniac playstyle, but there is more to this approach than the traditional maniac. Spencer would do this for the entire first orbit around the table of the game, but then switch to TAG or NIT for the rest of the game. This first orbit was obviously costly to him, but he treated that orbit as an "investment" to "fire up the table" because players wouldn't catch onto the fact that he only did this craziness for the first orbit, so the table would be "fired up" for the rest of the night! Just spencer sitting down at the table sometimes got players to wider up to hands they wouldn't normally play and to also get them
bluffing with situations they wouldn't usually find themselves in. While everyone is trying to combat Spencer's wild table image, he has already switched to being a TAG or NIT and Spencer would get paid the maximum when he picked up big pairs like QQ, KK or AA.
*I'll add that this "Small Ball" approach was not invented by Negreanu - just popularized (in big part by lowering the open-raising size to justify opening a wider range of hands)
There are probably a few more player types I'm forgetting too
I will note that some of these generic categories can overlap though. For example, a player could be both a good LAG player and a Reg. Similarly, someone playing "LAG" might not interfere with the same player also playing "Exploitative" (perhaps exploiting a tighter table) etc.