1.) Mirai historically has not gotten a lot of nationals inflation from US judges or much benefit of the doubt at Nationals for some time now, and even when she made the Olympic team and skated out of her skin, she still got hammered with URs and her scores weren't all that high. This is why I placed her in the score ranges I did, because I expect others to get more inflation in PCS and more leniency regarding the rotation of jumps than she will. Doesn't mean it will happen, just going off the patterns set by the past few years at Nationals.
2.) Christina at Skate America was coming off a 7th place finish at JW, a lackluster season in general that included 5th (with just okay skates) and 10th (with two nightmarish skates) at her GPs, then at Nationals she did well to place 5th, but she was a distant 5th and her score was not all that high. Plus she had vocalized the possibility of retiring after last season - in other words she was not in high stead going into SA, I don't think anyone was expecting much from her there, and then she had to skate 2nd in the SP after Rachael had set the score bar very low. Her scores there, IMO, were a bit lowballed for how she skated, I think simply because no one expected her to skate that well. But then she skated well at TEB and made the GPF and had a respectable showing there even though she did finish 6th, so I think Christina's stock has risen significantly since SA, and I expect her marks to be a bit more generous because of it.
Further, Christina historically skates pretty well at Nationals and gets decent inflation. Remember, back in 2011 with that very ugly 2a she scored nearly 60 points for her SP, granted she did 3f-3t, but still, she's improved a lot since then and her score would have likely been 60+ had she gone clean then, so now, I think low 60s is definitely possible if she hits the 3t-3t and is otherwise clean. Then in the FS, if she tries her 3f-3t again, which we know she is capable of even though it wasn't great at the GPF, she'll be going for a 7 triple program, and her jumps are nice, apart from the lutz the jumps should get decent +GOE, and she's also cleaned up her spins as well. Christina also has that new, fresh, exciting thing going for her which Mirai does not, so I tend to think, with the fall international season she's had, if she delivers, she'll be rewarded. I still think a clean Ashley and Gracie would definitely beat her, but I'm not sure about anyone else.
Also notice I did put Agnes in the higher scoring group for the SP - because I think she can beat a clean Christina, and Mirai, with a clean SP, I just have doubts about the FS. Sort of the same thing for Mirai, at Finlandia she was strong and got 110 for her FS, then she skated decently but with a lot of URs at CoC and scored 103, at NHK she skated what seemed to be a flawless program and only scored 115, so based on this and Christina's 117, 112, and 106 for international FS scores this season, I tend to think their FS scoring potential is similar. Then for the SP, they have the same planned content, and Christina's short, IMO, is gorgeous, while Mirai's is good but not great and a bit lacking in transitions for me, so I tend to think their marks for that should be pretty much the same should they both skate clean.