I don’t know how and why you heard that crap about cycling being difficult…
The roads for cars are not always in the best shape in Belgium, but then, those are not the ones you’ll be riding. I have rode many Dutch asphalt roads for cyclist, that looked nice from far, but where in a much shittier state than your average Belgian road. Specially when it’s lined with trees, feels like off-roading in paved roads…
The connection bike lanes along the national roads from town to town are mostly sweat in the Netherlands. But the bike paths in little town centers are on crap stone paved roads, usually.
Cyclist don’t get the right of way in Holland. Maybe in city centers.
In Belgium, as long as you’re on a crossing at an area where there’s a pedestrian crossing, you’ll get the right of way. If it’s only a cycle crossing, cars will make you wait, or not.
Technically, the weakest link in public road users, always have the right of way. So at an intersection with no lights, or at a roundabout or a circle, when using the bike lanes, you can just go. Cars will stop. Unless it’s a dutch or other foreign plate, they have no clue.
From plotting a quick route, you have a couple of options.
Once you get into Belgium I recommend taking fietsroutes or fietsostrades for the long boring stretches… Literally cycling highways.
To find more bike friendly roads you can plot a course via a thing called fietsknooppunt. It’s a network of cycle lanes, sometimes along an existing road, usually on it’s own, out in the field. These extend into Holland. You might want to use these to plot a course.
I recommend following canals. Usually the straightest way, with good asfalt. Usually these are bike and pedestrian only.
Brussels became much more bike friendly since the introduction of a 30km speed limit in the center. Not claiming it’s perfect. It is city riding so some level of assertiveness is required to navigate the city jungle.
I am Belgian, cycle all over, in Belgium and Holland.
Do follow the required covid-19 measures.
Enjoy, don’t crash. Good luck.