Jax, Irelia, Fiora, and Camille are all very similar champions, but their small difference determine what situations make them strong.
Jax: Jax has the ability to dodge all AAs making him great against AA champs, and as such kicks Camels ass, with a nearly no counterplay stun. His ability to deal large amounts of physical and magic damage make him hard to build against, and he is a better duelist than Camel, he can push lanes and take turrets faster than the others. He has a gap closer that can target anything, allowing for ward jumps over walls, to enemies, or to allies
Irelia: Irelia has a resetable gapcloser making the distance she can travel insane, however unlike Jax it can only target enemies, which means it is harder to use to get away, and very unlikely that she will be using it to go over walls other than to JG monsters. She deals all three types of damage unlike Camel who only deals physical and true damage, Irelias CC is also way more reliable as it cant be dodged and lasts way longer (twice as long). Her ability to kill an enemy back line champ in a team fight and live through it is way higher than Camels as Irelia can jump in and burst down and ADC or APC before they can react, and then still have the sustained damage to be a threat to the rest of the team, without being able to be effectively CCed thanks to her passive. Irelia also has a ranged ability as her ult that heals her for huge amounts and can be used while moving letting her chase or kite back away from an enemy all while healing. Irelias ult also allows her to use Triforce better than Camel, not worse as it gives 4 casts that can each be spaced 1.5 seconds apart to get 5 procs of triforce in a fight rather than the 2 or 3 that camel gets.
Fiora: Fiora has a very short cooldown gapcloser as long as she hits an enemy, but it can be used without any target making it great for going over walls if need be, or for dodging abilities, Fioras stun is very unreliable, but can potentially be way more potent than any of the others as she can block any ability in the game with it, she deals a huge amount of physical and true damage and can outduel most other champs, and with a proper use of her Riposte can even stop Camels ult from going off while still putting it on CD
Camille: Camilles gap closer is longer range than any of the others, but the first part has to be aimed at a structure/ wall of some sort, and if the second portion doesnt hit an enemy champ she does not get to stun them, her gap closer is also on a higher cooldown than any of the others. Her ability to catch and kill high mobility champions with her ult however is much better than the others making her great against champs such as yasuo, katarina, and kassadin, while the others wouldnt be able to keep up with them. Her long CD on her gap closer makes her easier to kite than Irelia or Fiora when her ult is on CD while Irelia and Fiora are potent killers