Oh god, honestly, just be breezy about it, both to yourself and to your child. Allocating too much brain space to this is a fast-track to madness, you have another 13 years of compulsory education to get through, in the course of which you will encounter issues that definitely will require you to intervene. This is not one of those.
If nursery have said 'it's fine', I would read that as 'pilsbury's dd is a confident, sensible, well-adjusted child who will flourish in any setting', and recalibrate your mindset accordingly.
For a child like that it is actually much better to have access to a range of possible friendships outside established nursery ones - some girl-friendships can become quite clingy and restrictive particularly if one of the children has controlling or queen-bee tendencies, or alternatively is not that confident and wants to keep her existing friends a bit too close for (their) comfort. The mantra is, "Oh, aren't you lucky, you can make lots of new friends and still see all your old friends as well, how exciting."
Class allocations are a nightmare for primary schools, because whatever damn thing they do, there'll be some parents who are not happy with it, some of whom will kick off unpleasantly and unreasonably. Unless there are very specific issues, eg a vulnerable child being placed with a child who has a track record of bullying them, then it is ALWAYS better to assume that the school have made decisions in what they think are the best interests of all the children, and that it will all work out just fine.
I can absolutely guarantee they will not change the class allocations in response to anything you might say, short of some dealbreaking reason such as your child being in a wheelchair and the allocated class being up some stairs for eg. Not only will it not achieve aything, but you will get on the school's radar as a complainer before your child has even started, which is baaaad tactics. You say you don't care about being seen as 'one of those parents', but you actually don't want that reputation because, as someone has already pointed out, the school will be much less likely to take you seriously when there is an important issue if you have form for kicking off over minor stuff like class allocations and how often the reading books are changed.
Honestly, trust the school, trust the teachers, be the parent who is super-supportive and enthusiastic about what the school are doing, and always thanks the teachers when they've gone beyond the call of duty. And then when an actual issue does come up that really needs to be taken seriously, the school will be much more likely to take your input on board, because you will have a reputation as a sensible supportive parent rather than a complainer.
It's a looong journey, keep your powder dry.