It depends on what your goals are with chess. If you would like to see incremental improvement in your game, play slower time controls and study your mistakes. And if you don't care about improvement, play lots of short games and have fun.
Should I only focus on rapid or play rapid, bullet and blitz all equally
But time limits take that all away.
Focus on lounger games until you hit a peak and then only play rapid and blitz after this - bullet is never good for anything and rots your brain, best ignored.
Should i focus on only one time control or others also?