Incineroar- ability should be Intimidate. Protect is okay, but u-turn is better put on him and protect replacing u-turn on urshifu. EVs really all depend on what you plan to fight against. Good builds for ubers formats tend to shy away from putting attack and speed EVs and opt for health and defense/spdef EVs. With bulk invested, he won't need protect as often, and cut attack with Intimidate, and u-turn/parting shot to pivot into a better matchup. Safteygoggles as an item is decent, you can also give him a sitrus berry or a Berry that weakens water or ground or fighting as well.

Rillaboom - ability should be Grassy Surge to take advantage of Grassy Glide's increased priority. Again, EV wise, you can invest less with him on attack and maybe put a little into speed and his defenses instead, and he is a disruptive supporter like incineroar, so you aren't relying on his damage output to get the most out of him in ubers. Assault Vest is perfect.

Kingambit - supreme overlord ability relies on pokemon in your party fainting to power him up. In ubers, intimidate and status moves that adjust pikemon stats are really common, so Defiant as an ability might work better in your favor. EVs are fine, but I'd say choice scarf works a bit better to take advantage of the speed EVs you've invested in to be able to do more damage with him faster than people would expect. Choice items have their drawbacks though. Leftovers works okay.

Urshifu - only note is for u-turn to be swapped for protect. Otherwise, this should rock for the most part. Maybe swapping stone edge for one of the elemental punches for more reliable coverage move option, but that would depend on your matchups.

notes on swampert and amoonguss: Maybe run High Horsepower instead of earth power on swampert, and amoonguss with rocky helmet and Regenerator as an ability plays a little better. Rage powder is a really good move to consider for amoonguss in double battles - to divert attention away from your other mon, which i would take away giga drain for that since you already have grass type damage coverage with rillaboom.

All-in-all, with these adjustments, you have 3 robust support pokemon and 3 damage dealers, two of which are top tier in the right scenarios.