Yes.
I've been using Wear OS devices for a few years. I've had 3 watches paired with one phone, most recently this Note 9.
I wanted to move to Samsung watches, because I was tired of the Wear OS lag. I contacted Samsung and asked if I could pair 3 watches with the same phone. Their answer was yes, but only using one at a time.
I currently have a Gear Fit2 Pro and a Gear Sport paired with this Note 9, successfully. The only issue is that when I switch watches the NOTIFICATION ACCESS for the GEAR WEARABLE app gets turned off. I get a notification and have to turn it back on. It's irritating, as Wear OS devices do not do this, but it's a minor inconvenience.