I’m in England, my longest friend has an Android device. I still text him in the Messages app. He’ll use WhatsApp when sending pics and links, but I’ll text him normally always, I prefer that over WhatsApp.

It’s really not a big deal. Use whatever app you wish. Apple doesn’t need to support RCS

You’ll need to upgrade to a new iPhone. watchOS 10 requires at least an iPhone XS

I use a MacBook for basic needs. I have an 8GB M2 Air, I don’t really need a MacBook for what I use it for, but I’m in the ecosystem and enjoy what Mac has to offer within it, I love knowing that if and when I’m ready to push my MacBook further, I’ll be able to comfortably. 8GB is enough for me and likely always will be enough.

Everybody of course is different, but I’m an average user and it’s more than plenty for me