This is pretty much how Jigglypuff's Metagame works.
She gets you up to 100% quick by doing throws, pounds, tilts, dair, and b air. And then kills you with a fresh f air which kills you before you get to 120% (saying that your a middle weight). Some times though you'll get killed earlier by that by a rollout, even a rollout charged for less than a second has the power to kill some1 around 60%. Jigglypuff could gimp a player as well, and finally she has rest, which she can punish rolling with and do drill to rest, and its unavoidable if the opponent trips by the dair. The downside is that Jigglypuff can mess up the fresh fair and will have to use other moves to be able to kill again, which wouldn't be till like another 20% or so.
Jigglypuff's biggest concern is stale moves. Her #1 killing move is the fair which won't kill if stale. A lot of her moves can do about 10-12% and have little lag. The Utilt does 12%, the f tilt (yes that tiny kick she does) does 10 friekien percent. And every one of her grabs does 10%. Each of Jigglypuff's pummels do 3%.
Jigglypuff's grab game is a beast. Like, her dash grab goes 3 character lengths its so long. Jigglypuff's throws have little follow up so its best to rotate through each one. If an opponent is excpecting a drill to rest combo you can grab them after drilling them.
Three of Jigglypuffs moves are some of the longest lasting moves that shouldn't even last that long. Her dair but its supposed to be that way, the nair which stays out very long and can go through air dodges, and pound, the longest lasting, long range, sheild breaking, move that *****. Jigglypuff can angle the pound up or down and that makes Jigglypuff travel even further. It also it cuts sheilds in half and breaks thoughs that are less than half. Its downside is that it has a big cooldown time and can be sheild grabbed out of it.
Rollout is one of the most quickest powerful attacks that can be kill without having to fully charge it. This is one of the moves that makes games cruical for opponents who don't know how to fight a Jigglypuff (which most likely will be many since Jigglypuff is low tier). If you think you can just shield it and live your dead wrong, Jigglypuff can turn her rollout 3 and sometimes even 4 times, the result of your sheild will either be a sheild poke death or your sheild breaks and then you die from a fsmash. Trying to counter it with Ike, Marth, or Lucario's counter won't work either, rollout is fast and it just goes right by before they can hit with their counter, and by that time Jigglypuffs turned around and hit you with a rebound. If players know the match up then rollout won't be as effective because they'll know how to avoid it.
Jigglypuff also has many good stages that she can choose from in tournaments.
Delfino Plaza - Sharking and Rest Canceling
Brinstar - Sharking and Stale Removal (by hitting the stage with attacks like n air to refresh f air)
Frigate - Gimping
Castle Siege - Stale Removal
Japes - Gimping
Even stages like Smashville and Yoshi's Island there Jigglypuff can use stale removal by hitting the ballon or shy guys.