With non-Apple Watches, you can't 1) reply to texts, 2) answer phone calls (or place calls), 3) interact with other native iPhone applications (like Apple Health).
You'll pry my Garmin from my cold, dead hands but there's no mistaking it for an actual "smart"-watch. I value it entirely for health & fitness, and the very few "smart" things it can do are just nice-to-have icing on the cake.
You can! I use my garmin a lot to switch songs on my iPhone, change volume, etc.
But like the other commenter said, you can’t reply to notifications or calls when the watch is paired to an iPhone, but you could when paired to an Android, which is a feature I definitely miss from when I had a Pixel.
You'll pry my Garmin from my cold, dead hands but there's no mistaking it for an actual "smart"-watch. I value it entirely for health & fitness, and the very few "smart" things it can do are just nice-to-have icing on the cake.