a hard tail 29er is your best option for the things you describe and putting proper wheels on it is going to be a huge factor. IF your going to be riding it on the road a lot, you don't want very knobby tires on it but depending on the types of offroad trails, you may need to get knobbier tires! Quite honestly, most will tell you that you really want 2 bikes for these purposes but it's not impossible. you could consider a CX bike which will be very fast on the road and on fire trails but absolutely will be a no no for any serious MTB riding.