@vision blue to reply to one of your last points first.....unfortunately, I too am noise sensitive though I react to some noises negatively more than others. It is an issue that worries me for sure, as there is so little control over neighbour's noise and modern flats I know can be particularly bad for noise if they are not well built. I would not move into a normal block of flats for fear of all night parties etc, or a neighbour who liked to play loud music.
In a retirement flat I think it reduces the chance of some kinds of noises in normal flats, (loud rock music/loud quarrelling couples - both of which I have endured in my lifetime!). I did ask my son to check for this factor when he was looking at the flat for me, but of course that is just a snapshot visit. The flat that I have bought will only have a neighbour one side of me, and one above, and the bedroom is not next to the party wall, so that would only be affected from on top, so I am hopeful it will be OK. The other thing is that there is a manager on hand 5 days a week so if there are any very severe issues of noise, hopefully I can raise them with her and she will help to sort them out (something not available in a normal flat).
In my current house with footpath, I do thankfully get grocery deliveries OK (I bet the shop people hate my house as it has a long sloping path downwards and they often carry the baskets for ease), and the post delivers to the door. The parking issues (not possible outside the house due to the footpath), was definitely a factor in trying to sell the house, as people love their cars and want to keep an eye on them! When we moved here, we saw lack of cars as a bonus as it is quieter and less polluted! My new flat is around the back of the building and not near the car park and the road is not busy so that is a a bonus.
Today I have someone coming for probably the last item I will try to rehome - a rather tricky niche item that cost quite a bit - a hand made wooden rag rugging frame!! I think it could be adapted for embroidery use as it comes with large clips that I bought separately. I live on quite a poor estate (with a stunning view - see my profile pic), and some of the the items (like my late husband's wellington boots) have gone to people who really appreciate the items for free. The woman who is coming for this item lives just up the road. They are not supposed to sell anything that is given, but I honestly would not mind if they did! The only reason I own my own home is due to luck (I inherited the house via my mother in law's inheritance money) and then more recently inherited myself via a cousin, and a little via my mother. I like to pass a little of my luck on to others.
As you are doing your own clearances, are you too in the older age bracket as I am? Now I am nearly 70 I suddenly realise how little of my life may be left. I nodded my head at your description of chucking away the maths equations - not that I have any of those, but things that once seemed so dear and impossible to part with have gone that way. Some went in previous moves (there were many at one time 13 moves in 13 years I think at one point). Some I cannot quite manage but maybe will down the line. I too have love letters and as they are between my late husband and myself, I feel I should keep them for my sons.
The 'need to have things a certain way' - the 'homeostasis' - is that due to the ME condition or another reason? I do find myself that as I get older, my anxiety levels increase with any changes and it will certainly take me a long time to navigate outside of the new flat. I have to plan endlessly when I go anywhere and I tend to be meticulous with any planning as my brain works so slowly now (hence thinking of the moving details!).