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In the end it really depends on what you find enjoyable.
Personally, I treat my gravel bike as my get-to-anywhere bike that's good for 100k plus rides but opens a lot of other options and route choices in comparison to a road bike. Usually I run 40mm ish tyres on 700. I have a second wheelset for it with so 650b tyres which allows me to take it on even chunkier bits, but since I bought the MTB that rarely happens.
My XC bike is great for techy climbing, natural trails, steep stuff and so on. But after 2 hrs the lack of hand positions get uncomfortable for me and the tyres I use are draggy anywhere that isn't single track, so it just ain't great for longer rides.
Also worth considering is the increased maintenance that comes with suspension and droppers.
Your ideal rig might be somewhere in the middle. Have you looked into flat bar rigid bikes at all? Like this list: https://bikepacking.com/index/rigid-steel-off-road-touring-bikes/
Cheers. Plenty of nice road riding around here and I can get around a bit on cx tyres. Just wondering if by the time you’ve got 45mm tyres on a road bike, an Xc bike might be more fun for exploring?