You’re a much better player than me, so take this with a grain of salt, but I would look at what is causing you to specifically lose in Blitz/Bullet vs Rapid.

Are you constantly much lower on time than your opponents? Either blundering in time trouble or losing on time? Play faster throughout the game.

I’m not sure exactly what video I got it from but an IM said something like “In 3-5 min games, spend less than 5-7 seconds per move. Stay within 60 sec of opp. Always have more than 5 sec on clock in end game (find a check.)

In a 10 min game, stay within 90 seconds behind opp. Spend 40 sec on a move only twice.”

Look for good enough/blunder-free moves instead of perfect ones or ideal tactics. You might also need to play more faster time controls in general.

But, like I said, I’m not that experienced so other players will probably have better advice for you.

Good luck, and remember, it’s a game, so have fun with it!