I often wear an open front double sling from OP/Tech when shooting events. I almost always have the "short" lens and camera body on the right side of my body and the "long" lens and camera body on my left.
Typically I use a Canon 5D Mark IV with an EF 24-70mm f/2.8 L (or EF 24-105mm f/4 L IS if the weather is a factor or I'll be in a rowdy crowd, or an EF 17-4mm f/4 L if I need the extra angle of view) and a 7D Mark II with an EF 70-200mm f/2.8L IS II. In low light I'll put my older 5D Mark III on the right side with the wider angle lenses mentioned above and use the 5D Mark IV with the 70-200mm on the left.
In extremely low light I'll go with something like an EF 35mm f/2 or 50mm f/11.4 on the 5D Mark III and an EF 85mm f/1.8 or, more often, an EF 135mm f/2 L on the 5D Mark IV on my left side.
Sometimes I might carry an extra lens in a pouch on my belt, but I usually leave all of my other lenses in my backpack bag. I'll switch when there's a break in the action or the activities move to a different venue, like weddings tend to do. I tend to not change lenses during the middle of any particular segment. I have, on occasion, carried a third body with a third lens on a more traditional neoprene neck strap (The one I got from Canon when I first joined CPS 'Gold") if I think I really need three different lenses. Four out of five times, though, when I do that I only use one of the three camera/lens combos rarely if at all. So I've learned to resist the temptation of letting that third camera get in the way.
Lately I've seen more wedding and "upscale" event photographers who use leather harnesses. I guess it sets them a bit apart from the crowd of other photogs? Some of them do look really nice, but I've never trusted slings/harnesses that only have a single attachment point into threaded tripod sockets that were designed to have compressive, not tensile, strength. Even if the tripod socket holds, most such design's weakest links are the little swivel pin that can loose the flattened head and dump your expensive camera and lens on the ground.
I wouldn't be willing to sacrifice the comfort, security of redundancy, and configurability of my OP/TECH Double Sling Neoprene harness. But that's me.