To be honest it was an easy transition. The Apple Watch I had was a few years old so didn't have all the functionality newer ones had (like the always-on display and new sensors), so in most ways, the TAG was an upgrade. The only smart features I lost were those I had no interest in on a watch anyway, like making and receiving calls on the watch and answering text messages. I've always been pleasantly surprised by how well it works with an iPhone, at least until this new upgrade which has taken away Wallet.
There's no doubt the TAG is a much better-looking watch - friends with Apple Watches think the same. I doubt I'd be tempted to try an Apple Watch again.
The only difficulty transitioning was down to TAG's very poor instructions but there was enough help from here and TAG's support team to get familiar with it fairly quickly. I'm going to say it's more like 50% smart device and 50% nice watch.