I am sure this is a numpty question or query but here goes

I have a 29er been riding mainly road and firetracks with trail centre thrown in but would like to undertake some sportifs for fitness and distance training. I do not want a road bike as due to nexk and back injuries just about coping with a 29er.
I would like to reduce the rolling resistance from my 2.4 and 2.3 tyres down ro something more road friendly and quicker. In this I would like to keep some cushioning and franly skinny tryes scare the hell out of me, so would like some fast rolling but still grippy tyres.

So can I run 700cc tryes or cyclocross on 29er rims?
And
What are peopels recommendations for tryes ?

If their ETRTO is 622, they’re road-bike-standard size. You can fit anything from 700x23c skinny road bike tyres to crazy big 29er balloons.

Road friendly, quicker and very puncture proof, I’d recommend a 700x35c Schwalbe Marathon Plus. They’re slick-ish but have grip, they roll well and they are more or less bombproof.

If you want the ultimate in big volume 29er slicks then the Schwalbe Big Apples in 2.35″ size are ace. I use them on the road in my Fargo and love them. Fairly grippy and absorb any pothole a UK road can throw at you.

If less is more then there are loads of hybrid type tyres out there in the 37-45mm range – take your pick.