If Adrien and Marinette had received Vitaa and Shii instead of Tikki and Plagg , how would bem their relationship ?
I am assuming they would still have their same counterparts (Marinette - Vitaa, and Adrien - Shii); and that Vitaa and Shii have spent more time on Earth, meaning they are much more familiar with humans and Earth than they currently are.
For Marinette and Vitaa, I don't thinks would be all too different for their bond compared to canon. Like Tikki, Vitaa would be very warm and encouraging to Marinette, though a bit more motherly and calm compared to Tikki. Vitaa would probably be very good with helping Marinette when she starts panicking and spiraling, and would be more assertive when Marinette makes her rash decisions.
As a hero I think Marinette would be hailed as more than a hero, perhaps even something akin to a deity with the power to bring back people from the dead. I think she'd be uncomfortable with this level of admiration, and there would probably be people who take it to the extreme. On top of it all there would be a moral struggle when it comes to her power, because it is unavoidable that people would be seeking her help because of it, and she'd have to deal with the moral burden of when she should heal and who she should leave to their fate.
As for Adrien and Shii their dynamics very different from Plagg and Adrien. Shii has a very bleak look on life, not exactly negative or bitter, but just very accepting of the bad things in the world and not optimistic of things getting better. This means Shii would probably struggle to be the emotional support that Adrien needs. Shii would care and he and Adrien would get along, but he wouldn't be like Plagg in terms of being able to distract Adrien or encouraging him to break free.
Sadly things wouldn't be likely to get much better for Adrien in terms of being a hero. There is a high chance he could get wings, but with the powers he has there would not be many opportunities for him to use it, and I think the world would only fear him for it. Both he and Marinette would be able to rid akumas of their negative energy (or he could also straight up kill the butterfly to keep it from escaping), but neither of them would be able to fix the city or strategically use their powers in a fight.
Now getting a bit on the dark side of things, probably the quickest way they could stop the akuma and prevent it from doing too much damage would be for Crow!Adrien to use his powers to kill the akuma, and once the butterfly was purified for Panda!Marinette to bring them back to life. It would be effective in theory, but I think the city would very much come to fear Crow!Adrien and just the idea of being akumatize, which would only add to the emotional stress being placed on Adrien and take it to the extreme. He would probably be very dependent on his kwami and hero partner to help him get through it all. Also Hawk Moth would constantly be targeting Panda!Marinette, as he only needs her Miraculous to bring Emilie back, and not both of their Miraculouses. This would probably add more pressure onto Adrien, feeling the need to protect his partner even more than in canon.
Basically a lot of moral issues would arise and it would be a lot angstier than what we got in canon.