I am just going to add on to the discussion. If you keep a single bird you will be their only social outlet, so of course you need to spend time with them. It is important to understand that this time doesn't mean 100% physical contact. It should be a mix of direct interaction and indirect interaction. You want to empower your bird to find interest in their play areas. You must provide intellectually stimulating activities such as foraging. You can read a book or work at your computer and your bird will explore, forage and play. Your bond is being busy and doing things as a flock. This is healthy interaction. Your bird will be an independent, confidant adult animal. Physical touch is only a tiny part of interacting with your bird.
In terms of keeping more than one parrotlet I would be cautious. As already mentioned, they can kill each other. Parrotlets swap mates in the wild and you have NO guarantee things will always work. You need to have a large cage for each parrotlet. If you have the space for multiple large cages I support getting two, but if you don't have the space don't risk it. I will tell you my personal experience. My parrotlets fight intensely. They each have their own flight cage and cannot be out together. My partner and I worked out a system for the two of them, but it is a fragile business. My bolder parrotlet has bitten, dislocated toes and shredded feathers on the other parrotlet.. and this was in the common play area. Sometimes parrotlets can get on great, but they are very territorial and they can't help themselves. That said I love my feisty little parrotlets. They are very affectionate to their person and wonderful fliers.
I hope my experience helps you decide.