I've ridden from Hoek as far as Leverkusen, where my mother in law lives and we often stay, and quite a lot in the Leverkusen area.
Your route to Leverkusen is a bit different from mine but does intersect here and there, eg crossing into Germany at Kleve.
I'm sure there are many good routes through the Netherlands, but where I found it got less pretty was on the fringes of the Rhur conurbation. Your route is mainly west of where I went - I was closer to the Rhine, via Xantern. My route was OK but then got awful - lots of poor quality cycle track on pavement on boring, flat suburban roads - around Krefeld. You may have got a good route through there but, if not, I would be concerned about the section from Krefeld, all the way through to where you hit the Rhine in Cologne, being largely busy, nondescript suburbia.
The Rhine from Bonn south will be pleasant, although you may find you have had enough of it at some point!
The bit that I know best is the Bergish Land / Sauerland, which is the area of low / medium hills to the East of Dusseldorf and Cologne. It's very pretty and, given proximity to big cities, surprisingly quiet. You could certainly find a fun 200-300km in there, while missing out what I think would probably be a dull strech from Krefeld to Cologne. You could do worse than cut across from Krefeld to Wuppertal and then follow much of this 200km audax route I did last summer (would make most sense to reverse it)
https://ridewithgps.com/routes/37135527You would then cut back to Bonn or Cologne from an appropriate point such as Dieringhusen or Wipperfurth to pick up the Rhine.
A bit later on you go across the first control of this year's TCR. The parcours there is promised to be very pretty, so you might fancy following a bit of that:
https://www.komoot.com/plan/@50.8097320,14.1483800,9.000z?sport=racebike&waypoint=hl:3901972I hope to know more about this bit by the end of July!
Good luck with the ride!
Edit
This is my route from Hoek to Leverkusen, for reference. I had some input from a friend who has ridden it a couple of times before. I would recommend it, apart from Krefeld-Dusseldorf.
https://ridewithgps.com/routes/5667370