Depends, my oldest girl has a coat and boots; she's a shorthair, ice can be sharp, and -30C is fucking cold.
Anyone who thinks that's silly can come here in the winter, strip down, then run out in the yard to shit.
As for decorative clothes, whatever. If the dog doesn't mind, neither do I.
I like putting some clothes on my dogs because it's funny and kinda cute. My male dog is used to it and doesn't care.
I will put a scarf on them during cold winter days.. They don't need it but I cannot resist.
It depends on the overall look and if it will help the dog. My mom has a little yappy shorthair that needs boots and a coat in the winter, while my newest will likely have a thick coat and be fine. I'm still making him bandanas and the occasional costumes though.