What do the off-road sections consist of? Are they just gravel roads/mostly-smooth green trails? Or proper rocky trails?
Unless proper rocky and with some descending speed (ie: steep gradients) in the mix I'd be looking at some 700cgravel tyres. Much lighter, way less wind resistance on the road sections, still capable of riding some mellow trails at a respectful pace.
I run 700x44c WTB Riddlers on my flat-bar gravel bike, and they're a pretty sweet bend of easy spinning on paved road/bike path/gravel roads, and while I wouldn't say they're great off-road tyres - they're predictable enough you shouldn't die unless you do something stupid. I've been quite surprised how well they grip tbh, but 0mm of suspension travel front and rear of that bike doesn't see me getting too adventurous with them.