I can’t answer about switches needing an electrician because I don’t have switches. some people can do it themselves and there are loads of YouTube videos showing you how.
I just use the smart bulbs and operate them via the Philips Hue App or the home app. I prefer using the Hue App. I also set up Apple shortcut widgets on my iPad for my favourite light scenes.
Lights or bulbs can be assigned to rooms; livingroom, kitchen etc and those can be merged into groups to control in one action, etc.
Yes you can use the + to Add accessories into the home app on any device that supports the home app and is running software that also supports being able to find said accessories. you can also use the manufacturers Apps to set up the accessories and they will be added to the home app. This is my preference. My bulbs have a serial number on them I needed to add into the Hue App. Some things use QR video you need to scan. Using Apple TV might be limited on what it can set up or edit but it can still be a Hub and you can just use your other devices to set things up. You can still use the ATV Siri Remote to control things.
Everything syncs using the same Apple ID. If you add something to the home app on an iPad for example, it will show up in every home app. The same way iCloud syncs.
Most of HomeKit requires a home wifi network but there are some things that don’t need this. you need it to control it.
it’s all a bit daunting to figure it out but with trial & error you will learn it. It’s best to do your research on which accessories you’re going to use for your needs. Also buy the latest generation on these products. Read reviews. BestBuy is a great place to read honest reviews. Reddit is good as well and there are lots of people helping on there too. As well as YouTube.
I hope that helps a bit.
