The Gavere in general works for me, yes. When I see the bikeinsights diagram I just think "is even the XL too small for me?"
Yeah, these diagrams are pretty abstract, I guess it's one of the disadvantages of trying to order something from halfway across the world. To put some more context around this, here's... another diagram, this one from xenograft's bike fitting tool. What it shows is where your handlebars would be if you used the same stem on both bikes; the red solid line is your Stevens, the blue dashed line is the FM336 size XL.
I assumed some numbers (e.g. your saddle height and setback), so take the following numbers with a grain of salt.
The first thing this shows is that on the Mondince your handlebars (with everything else being equal) would sit 18.3mm lower. In other words, you'd need to add some spacers on the Mondince if you wanted to match your position on the Stevens. Which generally isn't a problem unless you have a ton of spacers on the Stevens.
I made a mistake when it comes to the reach difference; it says 19.6mm but it's actually closer to 13mm (I forgot to move your saddle back to match your Stevens). So you need to compensate with a longer stem; again, not a problem unless you are using a very long stem on the Stevens already.
And you'd want to move back your saddle by about 7mm to keep your setback from the BB consistent (check whether you have enough space on your saddle rails).
Lastly, if you wanted to move from a more relaxed gravel position to a a sportier road position, the general wisdom is to go a little lower (no problem on the Mondince, since the frame is smaller) and a little longer (more of a problem if you have a pretty long stem already).
