Have ridden Ballyhoura- it’s very Daffyd Davies, old skool, narrow singletrack twisting through trees but not hugely technical. Good, entertaining riding.
Closest stuff I can think of and a top recommend is the semi-natural trails of Rothiemurchus, to include the Bothy Trail, Loch Morlich contour, bottom of Lairig Ghru, Feshie etc. Bothy Bikes in Aviemore have quite a few maps and lots of advice. Plus staying in or near Aviemore, you’d be very handy for Laggan, for a more built experience. Not far from Ft Bill too, where there’s loads of well mapped trail to explore in Leannachan Forest.
Another good alternative would be Drumlanrig, in the western half of the Borders. Definitely more XC than ‘Mountain’.
Enjoy.