Ah now!
Yes I suppose you are right. While I was writing the above I thought I might be doing this too early, I mean I'm not doing it for two years, if it was two weeks before the trip that would be a different story. I'll keep away from writing similar posts till closer the time.
As for experimenting in UK that is my plan, but can't do that till I get the bike and can't afford that till next year.
I just put "cycle innsbruck to Bolzano" into Yahoo and the third item on the list was a bike tour company offering exactly that route. You can look and see where they go.... They follow an existing (named) bike path. When I search for that path the 6th item on the list is a link to a website with hundreds if not thousands of long distance bike touring routes in Europe, all with GPS tracks and most with notes from people who have ridden them. **
This is really not difficult, especially when you're planning 2 or 3 years out.

In actual fact, it could turn out to be counter-productive if you end up giving yourself too many choices to make.
I find it highly unlikely that a map app would include fake roads to encourage people to use their app! It seems kind of counter-productive.
More likely the issue is in your settings. It might be plotting using MTB trails that other apps won't use unless you tell them to.
There are hundreds of posts here and elsewhere about the different apps, what works best where and how to optimally use them.
But this really brings me back to the point I was trying to make in my earlier post....
At this point all this stuff is academic.
Rather than asking someone on the internet if Komoot is good in Austria or not, why not try plotting a route near you.... and then go ride it! Get used to the app(s). See what works for you. What is useful to you. Go off route and see what happens. Switch off wifi and data and see how it responds.
Case in point. On another forum someone posted asking about navigation apps for Holland (I live here). One poster swore by Google Maps. It was great never let him down. He'd been on a self guided tour organised by a professional outfit. He had 2 days he was independent in a big Dutch city. That was when he used Google Maps to find the places he wanted to visit. Worked perfectly. Of course it did! It was in a city! There were no back-roads or fields or goat tracks.
Try using Google Maps outside of a city, even in NL, one of the best places in the world to cycle a bike and I guarantee you it will direct you through places that bikes will not go!
Google Maps is handy for estimating distance. Not for planning.
Advice on the internet is handy for estimating stuff too, but I wouldn't be depending on it!
On the whole app navigation thing - I find it useful to remember there are 2 aspect to navigation
1 Planning the route
2. Following the route.
Different apps have different strengths.
http://cycle.travel/map is one of the best planners in my opinion. You can downoad a compatible GPX or TCX file for your Garmin and away you go.
If I was in your shoes, I'd be making a list of all the places I wanted to visit and then look at ways of linking them all up.
I'd be looking to take advantage of any existing routes that are out there and then trying to link those up.
In parallel to that I'd be acquiring whatever skills I thought I needed - camping, navigating, cooking, cycling, mechanics, language etc.
I'd be dreaming about crossing the Alps and heading to Spain when November is howling against my windows. In July I'd be out on my bike dreaming I'm crossing the Rhine rather than the Tyne!
I get that you want to figure out how long you're going to be on the road to get an idea of your budget. But you won't know how far you can go in a day or a week (and still be able to enjoy the trip!) without actually trying it out!
Trust me, it's a lot easier to ride 150km in a day if your destination is a place you really want to get to, rather than another waypoint on a route you planned based on the cost of it.
** These are the two links I mentioned.
http://wheel2wheelholidays.com/innsbruck-to-bolzano-cycling-holidays
https://www.biroto.eu/en/cycle-route/italy/adige-cycle-route/rt00000095
No more spoon feeding