Tri98 Milly doing what she believes is right in moment without wasting time worrying over her decisions and whether or not they fit within her moral code is what makes her good person. Meanwhile, Vash has to funnel all of his actions through the lens of Rem's beliefs and severely chastises himself if he makes even the slightest mistake and hurts someone because being good is something he has to actively think about and angst over. Wolfwood points out they're both good people (in comparison to himself likely) in ep 11 but really Milly's the better person because her actions are her own.
I think that's why I hate when people conflate Vash and Milly as being one and the same in Wolfwood's eyes or, worse, see his sex scene with Milly as just his love for Vash being triangulated onto her. Because he goes to Milly for a sense of relief/forgiveness/understanding that Vash can't give him due to his allegiance to Rem. Even in his death scene, he projects Milly above himself and Vash almost like a religious icon.
Also it's Milly who gives Vash Wolfwood's punisher (a cross they're both strong enough to carry) and when he hesitates she assures him that it's what Wolfwood would have wanted. This act also felt like a form of forgiveness, like alleviating the guilt Vash has over Wolfwood's death just like Milly did with Wolfwood. But even outside of Wolfwood, it's Milly that recognizes Vash on sight and continues to call out to him when they encounter him. She also understands Vash enough to see through his happy facade in ep 12 just like Wolfwood did in ep 9. It's a shame there weren't more VashMilly scenes in the anime because they contrast each other in so many ways. (Moreover, them being together romantically is an interesting subversion of the standard interpretation of Vashwood because Vash would view himself as wretched next to Milly (just like Wolfwood does to him) and it would fun watching him process that in real time.)
All this to say it's funny when people say they love polygun in Tri98 because it always read as a superficial way to ship Vashwood and MerylMilly at the same time with VashMeryl and WolfMeryl on the side with like one reference to Millywood. But, when looking at Tri98, the real polygun is whatever is going on between Vash/Wolfwood/Milly because they're reenacting this image over the course of the anime...
While Meryl is mentally and emotionally in the cuck chair until the final episode of the anime where she comes to terms with her feelings lol
