Trying it out on an 11.9" iPad, I've got to say that the new tabs, in practice, are kind of a UI mess
You have several problems; the cognitive overload of "is it an address bar or a tab or both" coupled with the fact that choosing a new tab causes everything to move around a bit, and the colour blending is NOT helpful to distinguishing the tab/location-bar region from the page region. And, of course, you end up with
less room for tabs, as they are now sharing space with the location bar.
Still, it's (very!) early days, so maybe you get used to it? But... the initial feeling is that this looks good in a screenshot but may actually be meaningfully worse in-use. (And I learned my lesson last year about installing developer betas of macOS, so I'm leaving that well alone until it is officially released!)
On the positive side, tab groups are a nice feature.