I keep spare essentials everywhere too, as it's much more convenient.
So,
In the boot of the car I have a small bag containing a pack of wipes, 2 nappies in sacks, calpol and spoon,bib, a hand towel, a small blanket, water, granola bars, raisens, about £10 in change, vest and a gro,carton of formula and a bottle, clean socks, t shirt and joggers for my eldest.
In the changing bag is a bib, wipes, 2 nappies in sacks, calpol and syringe, small toys to keep baby entertained, purse, little flask of hot water, bottles and formula dispenser, snacks such as banana, granols bars.
Next to my bed is a pack of wipes, couple of nappes, a vest and a gro. (baby still in our room!)
Downstairs in a basket next to the changing matt is loads of nappies, pack of wipes, bepanthen nappy cream, small tin of vaseline, vest and gro.
I know the car boot looks a little too much, but I can't tell you the number of times I've popped out with one of the kids and ended up being caught in snow, traffic, etc. And in nice weather we are always out so I need to make sure I have the spare essentials.
So 20 vests and gros sound a lot, but it's not really. And it just saves you worrying about getting washing washed and dried quickly.
And yes, Summer baby is much better than a winter baby. My 1st was born 30th Oct and it was a shock to the system getting used to the lack of sleep and early mornings when its dark, cold and miserable all the time. Much easier when it's at least warm and bright and you can sit in the garden for the afternoon with the baby!
Can't have been that bad for me though as my 3rd is due the 1st November!
I can't get the link for some reason for the snowsuit, but yes I mean what you described. You can get thin non water proof fabric ones for Summer though, and I just prefer them so I don't have to worry about legs and feet feeling cold.
Don't pack one for the hospital though. Put one in the car and a small blanket, and when its time to keave your partner can bring whatever the weather requires!
One of the nurses showed me how to swaddle just using a normal blanket in the hospital, and my babies loved it too, but only for about 3 weeks, then it was time for the gro bags.
The vast amount of knowledge and experience out there is daunting at times, but if you follow your instinct and do what you think is right for your baby, the best way to learn things is through your experiences with your baby. Babies are different just as people are. So what one likes, another won't.
Sorry for such a long post!!