A cross country with a lockout would be decent commuter.
Probably the best mountain style for the road.
I would put small block tires on it.
They would have better grip, smoother roll, and longer life on pavement.
On the trail they do fine on hard pack and rock.
A knobby would be better on mud.
Full lockout is nice for the street but don't eliminate the adjustable as the stiff setting would be OK on the street.
The other style of bike to look at is a cyclocross.
It is going to be a better road bike.
It is designed for lighter trails.
If you just just look at one you would think this is not going to handle trails but it does better than you would think.
I know you are looking to narrow and not expand your search.
If you are going to commute 5 days a week and only some trail it might be a better style.
Something to consider before you lay out ~1000 - 1500 euro.
Since you are newbie then I don't advise you go used but you get racers selling cyclocross every year or two so there are some great used values.
I know you want to narrow your search but you also have bikes designed to fit in the middle.
This is a bike to consider:
looking for the efficiency of a road bike with proven off-road componentry
There are so many styles of bikes now that it is hard to decide. Bike shops will help you select the proper bike and fit you to the bike. As a newbie I would not decide over the web and order online.
In a comment you asked about efficiency (and distance). Distance does not affect efficiency. Over a small distance efficiency is just not as big a factor. I am used to miles so will report in miles. That is about 12 miles. So at 12 mph it is 60 minutes and at 14 mph it is about 50 minutes. You should get a 2 mph bump on a cyclocross (for me it is 3-4 mph). So a difference of like 10 minutes. But you may want the exercise. Not all of that is the style of bike as the cyclocross is also going to have more narrow tires. On a longer distance the drop bars are are nice. You can vary hand position to spread fatigue and more aerodynamic. For your commute can go either way. But if you want to go on some 40 miles road rides then cyclocross (and some more road type tires). I have done 100 miles on my cyclocross (with road tires).