I personally love multisites, because you only need to make updates once on core, themes and plugins. It also saves on hosting charges and makes user management easier. It also keeps uploads, posts, pages and custom content separate.
I guess you question comes because of having sub-domains (e.g. weddings.website.co.uk) or sub-folders (e.g. website.co.uk/weddings). I hear that sub-domains load slower that subfolders. According to the question on sub2.sub1.subdomain.domain.com your sub-domains can be www.commercial.website.co.uk or www.toys.commercial.website.co.uk as you wish. Most people prefer to make the URL as short as possible so that it’s easier to remember.
With Bitnami (Free) you may now have a multisite with separate domains (e.g. weddings.co.uk) controlled by one main website. You will need to run your own server for this (Google Console or AWS).
There’s also MainWP (Paid Extensions) which has you install WordPress separately on each domain and control with a main website. This will work with shared hosting.