If you’re going to Tenerife then Valle San Lorenzo, up to La Caldera (the cauldron), Teide and the volcanic basin itself are all well known areas.
As for the poster above – bollocks (no offence) – Gran Canaria has miles of forestry and the North and south west side of Tenerife is almost all pine forests above 1500mts with hundreds of forestry tracks and gradients that make racers blanche! They run world local, spanish and world class comps there every year.
There are english and german tours that will take you out with their kit/guides in aircon minibuses or get a car, a map and have a look yourself.
I lived there for 12yrs so I’m speaking from local knowledge not holiday brochures.