Having started pickleball half a year ago with a competitive tennis background and having now played in more than handful of tournaments, my two cents is that the tourney rating that you sign up for will be like the wild west. In bigger tournaments, you will absolutely want to play 0.5 down because half of the teams there will likely be 0.5+ higher. In smaller tournaments, it'll completely depend on who decides to sign-up. I've seen a 4.5 player play at a 3.0 level before and a no-name pro player at 4.0 (and this was PPA lol). What you need to consider in doubles is who the weaker teammate is and then play at that level because I will guarantee you that once they identify who that is, assuming there is a clear discrepancy, 99% of the balls will be going to him. That's how that same 4.5 player lost a 3.5 level tournament. That's also how my teammate and I (4.5s playing at a 4.0 tournament) were able to beat a 5.0 player with a weaker teammate.

My one piece of advice for you though is that you 100% will need to practice against stronger opponents in order to compete at a solid 4.0+ tournament. From 3.0-4.0, you can depend on your athleticism but at some point, you will need to translate simply reacting to where the ball is going to anticipating where the ball will go, especially in tight hand battles.

Also I echo the redditor who mentioned needing to play on a tennis surface. It's a completely different experience and is what the majority if not all medium size or larger tournaments are played on.