Yep, this is a great thread, and I think there are some really great ideas floating around here.
For Trixx, I agree with the fiery trickster thing. While Alya is energetic and outgoing, she is a devoted friend to Marinette. Even though I feel like they might have bumps in their relationship, I feel like Trixx would be a good fit for Alya and constantly make her laugh, though sometimes annoy her with pranks and stuff like that.
For Pollen, I would like to also say I'm kind of at a midpoint between motherly, responsible, and vain, spoiled, but I definitely can see her being like a more confident Sabrina, a fashionista who is daring and not afraid to be strict on Chloé and serve as a voice of rationality. So while I feel like she could be vain, she could still be motherly and responsible,
Now that we're talking about Kwami having contrasting personalities, I actually haven't heard many people talk about what Nino and Wayzz's dynamic will be like. For me, since we already know both characters, I can already sort of envision it. Nino is sorta boisterous, a modern DJ, and a risk taker, and Wayzz has always been shown to be vigilant and cautious. I honestly think he'll be really confused at Nino's interests, kind of like when your Mom or Dad is confused about technology or pop culture. That thought just makes me laugh.