Under what setting you get this?
Road cycling using the app.
CT selected the same route but a different one had I selected "Paved only".
I've noticed Komoot gives very different results under "gravel" rather than "bike ride" setting.
As does CT.
(As an aside I don't see "bike ride" on the app. I see touring, road, MTB, enduro MTB & gravel)
The problem with Komoot for me is that it selects very dodgy routes even in road cycling mode. It tried to kill me in Nashville, putting me onto a shoulderless high-speed 4 lane road with crazy traffic. CT gave me a longer, hillier but much more pleasant route.
Also, I suspect it "adjusts" imported routes to fit its own maps if anyone plans to use it to navigate.
No planner is going to be 100% accurate all the time and everyone has different preferences in terms of road type, surface, climbing etc. so it's really a matter of figuring out which one suits you best.
As far as I understand it, both Komoot and CT use the same underlying data but the algorithms are different. And if you need to talk to the man behind it he's already posted on this thread!
For a long route such as you are contemplating I'd break it down into sections for planning purposes.
Having said that, I planned a trip from NL to Ireland in 10 minutes on CT and discovered only one slight glitch along the way when I encountered a wall in an estate that was easy to navigate around. It was my own fault that it was out of season for a ferry to cross a canal.
As I said above, I personally prefer to go to places that interest me but if I wanted a good route between two random points I'd trust CT over any other planner. Your preferences may be different.