So, getting right into it today with a very important skill all Magic player should poses; the ability to choose a deck for a specific tournament. Now, it can be a bit convoluted due to the large number of formats, so I will address each relevant format.
So with Standard I believe that deck selection is the easiest while also being the most difficult. The reasoning behind this is that there usually is a “best” deck to choose from, whether it’s a few or just one clear best option. However, if testing is done and there is a clear deck to beat the “best deck”; that is an option. To reiterate, in Standard it is best to play the deck to beat or play to beat the best deck.
Pioneer is when it starts getting difficult to choose a deck and predict the meta-game. Since there is a lot more decks to choose from it is best to pick a deck you are most comfortable on. However, I do think deck choice changes based on the tournament size. You wouldn’t play a really hard punishing strategy for a 16+ round tournament unless it is the clear best deck. Whereas at 5 round PTQ may be easier to play the good, but difficult deck and get wins. I believe this is honestly just due to mental stamina. Being able to win 4 rounds and double draw into top 8 is much different than having to play the difficult deck for 15 rounds at a Grand Prix.
For Modern I use a similar system to Pioneer. (I am a firm believer in just choosing easy deck for large tournaments, especially eternal formats). But in Modern there is even more choice in decks, which leads to easier decisions. If you only ever play one deck and know it lime the back of your hand, play it. If you are stuck, play an easy deck that minimizes variance.
To conclude, you can play whatever you want and still do well if you are good at the game, it’s just easier to narrow down the options. Minimizing brain power and variance is a much bigger deal in eternal formats than Standard, and is more relevant for Grand Prix and Player’s Tours than it is for smaller tournaments.