Tetris 99 lets you choose 4 different tactical options when you play. You have the ability to go with Random, KOs, Badges and Attackers, and switching up between the 4 as you play is certainly a good idea. A combination of all options will help you get further in the game, and certainly keeps the action frantic. Turns out the dev team actually had the idea to include another 4 tactical options as well!
In an interview with 4Gamer (translated by NintendoEverything), Director Ryuichi Nakada and producer Akira Kinashi talked about the other tactical options they cut from the game.
Nakada: No, originally there were eight, including things like ‘Defensive’ and ‘Slowdown’. From there we cut them down to the current four.
For example, in the case that someone with the ‘Slowdown’ option was put in a game, they would be paired with someone with the same tactics selected and battle each other one-on-one. There were a lot of people that thought this went against the basic ethic Battle Royale. With the ‘Shield’ mode, instead of attacking other players after clearing away your blocks, you instead create a barrier around yourself. The problem with this was that in playtesting there were those who only chose this tactic and instead of attacking simply defended themselves, leading to long stalemates.
Kinashi: What happened with the play testers was surprising. I knew there would be players who didn’t want to actively attack but instead avoid being attacked, but there were actually far more than I expected. The result was that the game dragged on so that one match could take more than twenty minutes.
A bit later in the interview, we learn that a second wave of DLC is on the way. Specifics aren't shared, but we do get a general idea of what will be released.
Kinashi: In terms of free content, the ability to change the appearance of your own Tetrominos and also choose your own emblem. Also from May 10 onwards, we’ll be adding new modes as paid DLC. The first stage of this is a mode to get those not yet used to the game ready for the online mode by competing against CPU players, ‘CPU Battle Mode’, as well as a standard mode for those wanting to play Tetris alone, ‘Marathon Mode’. I can’t talk about the second wave properly yet, but we also plan to add content that lets people enjoy playing with their family and friends offline.