Bless you :)
Yes I do think you are overthinking - but only to an extent. Sorry this ended up really long!
I don't think you will annoy people by just making the parenting choices which are right for you. Unfortunately sometimes (and I completely did this) it can be easy to fall into a way of thinking when DC are very little that there is one particular way that is better than other ways. You might say "Oh I don't judge others at all" but secretly you still think that the choice you make is the best way to do it, assuming that others make different choices because they don't know any better, and it can come out in the way that you speak about it. It can also be the case that you end up in a little "bubble" of "this is our way and everyone else is just not like us" which is actually really unhelpful as it cuts you off both from forming friendships outside the bubble and from considering other approaches, which often can actually be helpful. It's silly to write something off just because one part of it didn't appeal to you at one point.
You also (and I'm sure this will come as no surprise pregnancy hormones being no stranger to you at this point) tend to feel very vulnerable when your baby is little and quite emotionally, not fragile, but thin perhaps. It's very easy for something relatively innocent to tip you into feeling strongly this way or that. It can be hard to hide those emotions. Likewise, an innocent comment from another person can sometimes make you feel defensive, even though they didn't mean any criticism by it at all.
Lastly if you have decided on very set prescriptive things being the "best" way to do things (whether best for your situation or best for mothers/babies in general) just be aware that if it doesn't happen that way for some reason, you can end up feeling quite down about it. Not everything is under your control, and it helps to be okay with that.
So what to take from it - there is absolutely no need to keep your parenting decisions secret. It is however courteous not to expect other people to be interested in them. (Unless, obviously, you're having a conversation about parenting decisions!) I have changed my stance on this a bit but now I would never share articles on facebook etc which talk about a way of doing something as though it is the only possible choice and everything else is wrong. There is a lot of guilt in parenting already, and people are only trying to do the best according to what they believe and what other things they have going on. I've come to realise that there is actually a massive range of acceptable parenting practices, even including some things that are completely unacceptable in this country or that I personally would never, ever consider. The exceptions are any kind of abuse or neglect, of course.
It can be really useful if you find yourself thinking that another parenting practice you wouldn't choose is undesirable in some way to try and work out what it is that would make that practice desirable, practical, necessary etc. Whether somebody's situation is different to yours, their priorities are different to yours, or they are working off a different information set (which might not necessarily be less valid than yours). Rather than just writing something off, try to consider why someone might choose it. It just helps you be more tolerant and keep things in perspective. (It also helps with the guilt if you find out that the way you'd planned to do something actually doesn't work for you in practice.) Nb, it doesn't tend to go down well if you ask the question directly of mothers or on internet forums e.g. "I just don't understand why anybody would choose to [insert parenting practice here]". "Tell me what you decided to do in X area/situation, and what helped you come to that decision" is MUCH more neutral and doesn't imply that persons choosing X option are acting completely irrationally.
Lastly realise that people commenting or offering advice are, generally, just excited about babies and really want to share the things that they loved about babies and welcome you into the parenting "club". They aren't actually criticising or (most of the time) even judging you. They are just reminiscing about their experience. Sometimes they are curious, especially if you end up finding that you do a lot of things outside of the "norm" or you're always adopting the latest thing that parents of older children might not have heard of. When people come across something they have never heard of before they tend to ask questions and sometimes throw doubt at it because it's outside of their experience. Try to see it as curiosity rather than demands to prove yourself and these things will be easier to handle. Especially if you get into the "bubble" mindset I mentioned earlier, it can be easy to fall into a trap of thinking that there are "us" parents and "them" parents, and every time you encounter a mindset or suggestion which falls outside the doctrine of the "us" you see it as a hostile attack designed to make you forget your silly, unnecessary demands of the "us" group and join the sensible parents in the "them" group. It's just not like that. Most of the time when people make comments, express surprise, ask questions, make suggestions or talk about how they do something it's not that they think you should do exactly the same as them, and it doesn't mean that you need to explain or defend yourself. They are just sharing their experience, or asking you to share yours and that is all.
This ended up really long, but it's what I wish I had known before I had DS. I was completely in the "bubble", and I was totally unprepared for the way I'd feel about comments, that, looking back, where nowhere near as hostile as I was interpreting them. I also cringe at how I dismissed advice out of hand which actually might have been relevant to me if I'd just actually thought about it or considered it properly. Yes, you will get unwanted advice, but you can smile and nod and ignore it, or discuss it if you wish. At the end of the day, it's your baby, your family, you're the mum. You (and your partner if you have one) get to decide. And short of abuse or sustained neglect, nothing that you do or try is going to harm your baby irreparably. Love them first and it will come right.
I wish you all the best with it :)