When you play poker, do you play according to a system, or do you pay more attention to the players participating in the tournament?
What you call system I call theory. The way the theory is applied is called methodology and this is present in any area of liberal sciences.
As others have said before, I play following the system and the psychological behavior of my opponents, i.e, I play the cards dealt and the sitting opponents.
And for that most of times we don’t need a HUD software, which in many cases can drastically affect our decisions to simple data analysis: read statistics such as VPIP, PFR, Fold to 3-bet, etc don’t turn us into winning players, for many times these softwares are incomplete information that bias our choices.
The most important is to have a dynamic range of hands
that will change depending upon the players sitting by our side at the table.
Most of professionals will say that we can open 15% hands from EP and barely 50% hands from IP (Hijack, Cut-Off and Button), however it is not so simple as the charts imply.
If we really open 15% of hands from UTG regardless or our opponents, we are going to suffer a bunch of 3-bets for value and for bluff
and we are going to fold a lot. We are going to get tons of calls of passive players and calling-stations, changing our odds
, once we open hands from whatever seat to have position, thus our intention is to get more calls from the blinds than from players in position.
That being said, sometimes we are to play only 5% or 7% from EP, for either the table is too much active or too passive. Many times we are not even to open raise baby pocket pairs (22-66) under the risk of putting blinds on the pot for nothing, once we will have to fold to a polarized 3-bet or for a calling station that have a very frequent C-bet flop:
Henceforward we are playing throughout the system and also playing our opponents.