For the Disney versions:
Ursula's base self is Wall level with only peak human speed feats, so she gets taken out by any of the named 21st TB competitors if she's even lucky to get that far. With the power of Triton (which by definition scales to him), she showed City level feats but was a complete glass cannon, being at best Large City level. As long as her/Triton's opponents are prepared, They wouldn't get past Akkuman. It's a similar case far Maleficent who showed Town level magic feats but could be taken down by a regular prince with a sword, having even lower durability and doing little better in speed. She might fare slightly better through magic hax, but again, doesn't really have a way of hard-countering Akkuman.
Kingdom Hearts versions:
They all get Star to Large Star level scaling from Zeus in both power and durability and are all FTL. With speedblitz and magic hax, Ursula could probably get past Cell, but has no way of hard-countering any of the Boos' regeneration. Triton fares worse due to lacking such hax and only really having water and lightning manipulation, so he probably stops at SPC. Maleficent has a ridiculous amount of magic hax that combined with her speed would probably allow her to solo the manga versions of Z and Super (especially due to not being affected by the laws of what realm she travels to), though stops Anime Namek Freeza due to the far greater radius of Namek's explosion in that continuity and the feat of Kaio not being able to track Goku and Freeza meaning he has what it takes to speedblitz and oneshot her.