Customs allowed wii fit trainer, charizard and palutena to make it to top 32. (not sure if gyw and rob used them.)
They add tons of new strategies for a lot of characters and that is amazing for itself. Cusstoms make the game deeper, competitive and more enjoyable in the end.
I ll list what each character usually gets from customs, these are only the most common ones and i might miss some.
2333 or 2332. Fast fireball, gust cape, explosive punch, high pressure or scalding flud.
Its a different mario, not insta better or anything, but it spice things up.
1311 or 3311. quick missile adds a better recovery for sure, the power of iceballs still in the air.
2312. Sleepy toad its good unlike regular, flying peach is debatable, and light veggie seems good enough.
3332. Fire Roar, dash slash, sliding fortress and turbulent bombs makes a more mobile and safer bowser allowing him to approach and land better. (this one being super important to him).
3311 seems good enough, little sidegrades but nothing major.
2311 luma warp and shooting star bits makes her just a little better, nothing truly amazing as some people make it out to be.
i actually prefer 1111, but some people claim 1313 grounding dash and big mechakoopa can shine.
1212. Speeding bike and rose scented waft make him slightly better.
3331. short orfer chef and Chain judge are little upgrades but just little. trampoline lunch gives him an amazing OOS kill move.
xx3x sure kong cyclone its very very good, but not gamebreaking as a lot of people believe. practice against it and its a non issue.
1121 rocketbarrel attack is nice to have sometimes, other time not so amazing. just another risky kill move.
1213. a better boomerang and meteor bomb. he gets a little better whirling leap is nice too if you like it.
1311. dins blaze is amazing edgeguarding tool. maybe im missing something about custom phantoms but i dont like them.
1111 or 1211. God save us from the all powered gravity granade not used in the grand finals at EVO. Seriously just stop prettending that customs make top tiers better.
2122. warlock blade, dark fist and wizard dropkick makes ganon more mobile and stronger. amazing upgrade.
2133 (maybe) IMO just sidegrades. fire arrow to camp, flying spin attack hits harder and short fuse bomb actually dont know.
1213 and probably more. relentess missile and mega bomb allow him to keep distance as the zoner she should be. Also can mix things up to trap your opponent which is really nice for her.
blast shot was used at evo, still not convincing. whip lash is ok at best.
guiding bow is ok at best, amplifying orbitars or impact orbitars depends on matchups.
2312. From bottom tier to top 32 EVO. Thank you super speed and lightweight, explosive flame is ok at best.
1123 is the best marth, sadly wasnt used. cresecnt slash makes his OOS and grab game very good, lai counter is the best non shulk counter.
2221. Close combat and aether drive patches his recovery issues. tempest is nice because windboxes. amazing upgrade.
3331. speed thunder and fire wall help a ton against rush down, gliding elwind is faster and less predictable way to recover and easier to spike with. Amazing upgrade.
3x3x. jumping inhale and particulary upper cutter makes kirby faster, safer, stronger. amazing upgrade.
x3xx bouncing gordo is safer to use, harder to bounce and allows traping mix ups.awesome.
1211 high speed drill is ok at best as a sidegrade. The big looser in a custom meta.
im no expert here but grounding blow its very offensive, safer and harder to react too.
xx3x twisting fox kills but it has slower startup and doesnt travel as far. risky.
xx23. fast fire bird makes him faster and allows more combos. reflector void its so good.
2311 thunder wave and heavy skull bash while good not gamebreaking as people believed.
1313 dragon rush is faster and safer, rock hurl allows him to land with super armor, very important.
1111 or 2111 snaring aura sphere is cool and all but default feels better most of the time.
1312. pound blitz and leaping rest true combos¡¡ yet nobody seems to care o well.
1111 or some custom shurikens tricks. still not impressed.
3x23 Zigzag can along with mega gunmen is the definition of trapping you opponent. duck jump snag is a little upgrade for having hitboxes.
1131 high speed burner allows more combos and safer recovery.
Im no expert but at least xxx2 psi vacuum works on non proyectile users.
2111 falcon dash punch is just a less powerfull but easier to land falcon punch. its ok.
1322. extreme ballon trip and timber counter allows him to camp on the ledge. Very powerfull strategy but no near invencible but you must practice this matchups. powerful but not gamebreaking as some thiought.
nothing truly amazing IMO. might be wrong.
2321 from zero to hero top 32 EVO. enriched sun, weighted header and jumbo hoop makes a low tier to very good character.
2332. Soaring tornado fixes his recovery issues, old one two killing move.
2123 or 3123 or 1123. As a shulk main i can tell you that advancing air slash is even more important than power vision. Regular, decesive or hyper arts seems to be player preference but each of them completely changes his gameplan. Huge benefit of customs but non shulk mains will not understand why and believe its for power vision, geez.
freaky fruit seems useful, as meteor trampoline but im no expert here.
so many options and almost all seems useful. danger wrap seems a nice upgrade in every case.
1211 hammer spindahs makes an already good move even better but just as campy. Good but not a problem.
Customs allows them to exist and be played. 3 more characters spicing things up.
Before saying that customs are cheap or anything like that inform yourself about what they bring to the table and only then open your mouth. Customs are not cheap, they help tons of character and allows them to fight face to face against top tiers, or to at least, have a chance.