Obviously there's more to how a character is played. If anything I was just describing Jigglypuff's flowchart.
Grim, do you solo Jigglypuff or do you have a 2nd main (not a secondary) to help back Jiggs up? If it's the former you should consider picking another character up. The main reason why I have so many accomplishments with Jigglypuff is that my Diddy Kong has allowed me to get far enough into tournaments to play and beat better players with Jigglypuff, because they don't expect a Jigglypuff player to get so far into the tournament and don't practice against her. There shouldn't be any shame in not being able to solo the 3rd worst character in the game. Think of it this way, want to solo Jigglypuff and get bodied in pools? Or would you rather wipe pools with a higher tier character like Diddy Kong, and save Jigglypuff for the games where Jigglypuff has an advantage against the opponent? Being good at Jigglypuff means you need to realize what matches are just not winnable for the puffball and vice versa. While I cannot survive without Diddy Kong, I can't survive without Jigglypuff either, as she has had to make comebacks in sets where my Diddy Kong had failed to win in the first match of the set. Both of them are my main characters, neither being the secondary.
The only reason why I wouldn't see myself as the best Jigglypuff player however, is that I haven't been very active in tournaments besides APEX.
As for my specific strategy, I usually like to play footsies with Jigglypuff in the beginning of the match, going for drill to throw combos, rotating throws to get the most damage out of my attacks. Depending on the character and player I'll go for a drill to rest combo once they get to killing percentage. Save my F-air and then get them into a situation where I can kill them at the lowest % possible. DON'T use Fair when they're onstage and don't have like over 130%. Even if you land the hit you risk staling it either because you didn't sweet spot it or didn't kill them, and after you lose that fresh f-air. It becomes a lot more difficult to kill your opponent. Get them off stage first, then land the hit as they try to recover.
Sure you can kill other ways but, because the rest of her moveset has such terrible KO power or is very easy to avoid (like rollout). You pretty much lost out on the stock battle unless somehow you've been avoiding trades the entire stock.