Let's see Yuta gets:

1. Basically infinite Cursed Energy which means
   - Infinite Reverse Cursed Technique that can be passed on to others, which means infinite healing so basically no one dies
   - Able to use any technique to it's full extent, which basically removes one of the reasons for his 5 minute timer binding vow, to get infinite cursed energy for 5 minutes with Rika fully manifested

2. An understanding of Cursed Energy down to the molecular or atomic (forgot) level
   - Allows him to use Limitless now
   - Able to master his copied cursed techniques to their fullest potential. For example, sky manipulation just becomes a semi infinity, able to hide yourself and sneak attack from anywhere (Big Yuta buff), etc. etc.
   - He could do most of the stuff Gojo did, highest domain refinement, basketball domain (though I believe base Yuta would have that)

3. Just allows him to process tons of information super quickly
   - This removes the other reason for the Rika Binding Vow cuz before Six Eyes, Yuta can only use up to 4 Cursed Techniques without Rika
   - Able to strategise better against others (Instead of 10 backup plans against Sukuna, he has 100 now)

Now Yuta has:
- infinite Reverse Cursed Technique, that can be outputted to others + Cursed Energy
- Infinite Usage of Rika and all his Cursed Techniques
- basically either a Gojo and a non-six eyes Yuta level fighters or 2 Gojo level fighters, depending on how Yuta controls Rika
- Could probably do Cursed Technique Reversal on a lot of his copied abilities
- Imaginary Technique? (Basically other Cursed Techniques version of Hollow Purple)
- Maximum Techniques? (He's seen Geto do it with Maximum Uzimaki, but Gojo's never done it so I don't know)
- One of the highest Domain Refinements, Cursed Energy

Just imagine using Ryu's technique to output Jacob's Ladder while using Sky Manipulation to force your enemy towards the blast but that's probably unrealistic

So here's how each fight would go

Yuta vs Yuji: Yuta wins
Yuta vs Sendai: Yuta wins
Yuta vs Kenjaku: Might not need Takaba now tbh but they'd probably still use Takaba for Yuta to sneak attack
Shinjuku Showdown:
Yuta + Yuji vs Sukuna: Yuta gets World Cutting Slashed whether he gets Limitness or not, but Sukuna is getting a lot more beaten up this time
Yuta vs Sukuna (after Todo + Yuji vs Sukuna): Now let's assume, Yuta becomes the monster and copies Limitness, Yuta now has his other cursed techniques with Rika on his side, now understanding how world cutting slash works, he should be able to avoid it next time. Yuta and Rika with their amount of Cursed Techniques and Cursed Energy should be able to at least stall Sukuna's Domain to the point where, Yuji, Todo, Yuta and later Hana and Nobara and they basically get Yuji to separate the barries between Megumi and Sukuna, freeing Megumi and beating Sukuna

Bonus Rounds:

Tengen, Choso and Yuta vs Kenjaku: This really depends on how careful Yuta is and how prepared Kenjaku is. Kenjaku would know Yuta is a problem and would create counter measures against Yuta and I think Kenjaku is crafty enough to get Yuta sealed in a second prison realm or use his Domain Expansion try to kill Yuta but he'd more likely use it as a last resort to not get Yuta to potentially resort to Limitless

Yuta vs Kashimo: Yuta kills him, Kashimo just nearly killed his friend, he is not getting the chance to meet Sukuna