For one, most people now spend most of their time in their browser or in a hidden browser (ahem, Electron?).

So unless you want something specific (video games, a Windows desktop app, ...), I think they just both work. I'm guessing even Linux on a mac is probably okay (since so many people have the exact same hardware as you...)

Yes, today if you text someone not using iphone, you will have a green bubble which means you are practically a pariah and get made fun of. In fact my circle almost does the same, but more jokingly because you make fun of each other cars at the older ages lol.