Gravel Bike on Road
Hmm… I’m not sure how often I use my gravel bike for anything other than road. Sometimes it’s flat paved roads,

often it’s rugged mountainous roads,

and some may have even been rail roads,

but few miles are spent on proper unpaved non-roads.
Being a derailleur-geared diamond-frame drop-bar bike oriented for use on roads, I don’t consider the gravel bike to be a not road bike. Perhaps it’s not, if “road bike” is used with a high degree of specificity, as in “pavement road racing bike” or similar.
But I’ve been impressed at how little the actual performance cost of versatility has been. It doesn’t feel anything like a road bike, but it’s good enough in the role that I sometimes use it on spirited paved rides for funsies. 2.1" tires and all.
I’m getting a new Orbea Terra. Was thinking of selling my road bike and investing in a nice set of road wheels (HED/Flo/Zipp). Orbea will have 1x.
Will I be really disappointed trying to make a all around bike vs 2 separate bikes? Current road bike is a Cervelo C-3. Also still have my P2C.
If you want to play that game, make sure to cover the low-hanging-fruit configuration stuff.
Posture is a big one. Changing fit between rides is obnoxious! If you like using your traditional road posture on gravel, then this is no problem. Otherwise, consider what you can and can’t get away with.
In my case, the klunker beach cruiser geometry of the underlying frame was almost a problem, but with a zero-offset seatpost, I managed to produce a fit very similar to my skinny-tired bikes.

Gearing is another issue. And it depends entirely on you, and your regional terrain.
In my area, the paved riding consists mostly of clumps of medium hills separated by flattish valleys. I like having everything that a typical current road bike drivetrain offers, including the tightly-spaced gears at cruising speeds.
But our gravel is forest roads in the foothills, and it’s mountainous. There are stretches that average over 12% for a mile at a time, on rough double-track The steep bits are very steep. Having a gear significantly lower than 1:1 is not a bad idea for me.
So naturally, I put together a drivetrain that satisfies all of those needs at once. A 3x8 setup, 48-38-24 chainrings paired with an 11-13-15-18-21-24-28-32 cassette.

Okay, so that’s really cheesy, but this bike is a concept testbed on a budget. And it works. 
Obviously your situation is going to look very different. By choosing 1x, you’re going to have far fewer ratios to work with than I do. But, you’re also planning to swap wheelsets between rides, whereas my bike is set up to always be ready for its full spectrum of use cases. Including rides that include everything.
If I was only riding off pavement, I wouldn’t care about the wide spacing; if I was always riding on pavement, I wouldn’t care about having a 19" low gear. If you’re okay with 1x on your road-only rides, and you’re okay with 1x on your gravel-only rides, you’ll potentially be able to find a good solution involving different cassettes on different wheelsets. This may get obnoxious if you also require a chainring swap to bring things into certain ranges, and/or if your rear derailleur just doesn’t shift perfectly across both setups without adjustment.
The other really big thing with low-hanging fruit is tires. Riding with tires that aren’t reasonably reasonable for a use case can be less fun. Rocky gravel can be alright on slicks, but mud roads really need knobs. And if your situation demands big knobs, this can make for worse behavior on the road.
I lucked out in that PNW gravel is mostly pretty rocky, not a ton of slop. I’m running wide performance-oriented slicks, the width handles the chunky stuff pretty well and the tires give up surprisingly little on pavement.
In your case, since you’re swapping wheels, this is unlikely to be a large predicament.
Why not just look at something like compass tires?
I use them and like them a lot.
The sidewalls are paper-thin, so I wouldn’t err narrow when choosing them.
Their puncture protection consists only of prayers and hope. This isn’t an issue for the wilderness roads out here, since most aggressive stabby things in the region are human-made. I ride over blackberry thorns all the time, and they never go through. But in goathead country, I would guess that tubeless is mandatory to seal pinholes.
Their greatest asset is acoustics. When pavement drums my Rat Traps, they let out a soaring roar, IMO the finest road slick hum I’ve ever heard.
I don’t have any direct experience with the Rene Herse knobbies. I’ve met a couple people riding them, seemed to like them.
Steilacoom is probably a strong contender for most oft-mispronounced tire name.