You can truly be world class with any method. It varies person to person--for example, I was grinding flip for years and plateaued once I hit sub-6. It just didn't work for me, so I made myself switch to noflip 7-Simul (Tommy pin order/memorization), which allowed me to become mid-low 4. You can still be sub-4 with flip, and there are multiple people who have hit that skill level by optimizing execution. You can become fast with Sheerin, but very few people use it since 7-Simul became popularized.
I actually advise against getting into one clock method with the intention to switch soon after. The faster you get with one method, the longer it will take you to get used to another. I wish I started 7-Simul sooner, because it took months to get faster than I was with flip. But again, I pursued 7-Simul because it had the potential to get me past my own personal flip plateau. Just know that 7-Simul or 7-Simul flip will take patience to learn and you'll DNF a lot at first, but that's just part of it for everyone.
If you currently use flip, I would say you should use that for your upcoming comp. Getting good enough to comfortably use 7-Simul officially could take a little longer depending on how much time you have, but if you want to try a different method, it never hurts to look at some tutorials and see how you like it. After your comp, you could either keep grinding flip or try another method--the possibilities are endless! If you actively practice before your comp, you couod easily be sub-12 (or sub-10!). Best of luck with clock!
