I just wanted to ask your opinions about those strategic games. I was thinking about to play something like chess. 

Sorry, but teamfight tactics is likely a big no-no. Strategy video games are still video games and they will still release massive amount of dopamine with flashy onscreen effects, an ever changing game with patches and the likes, not good at all. Add the fact that it was made by the same company who created one of the most addictive video game on the market and I would really stay away from this.

Chess is a special case, because it was a board game originally and not a video game, but playing it online could be harmful and as addictive as other things. It depends how you approach it, what do you gain, what do you lose and why are you doing it.