For people interested in soundproofing it's probably best to have a multi-angle approach, like most headphones today. They don't focus just on being louder than other noises but on blocking them too.

I find it's not so much the small spaces but how shitty the construction is - hollow core doors, large gaps around the door, thinnest possible drywall, etc. Changing to well fit solid core doors would be a big benefit. Then of course there is old noisy bathroom fan to cover most remaining noises.