Im there in Mastricht. I did a reconnaisance a few months ago with a buddy who is also starting:
https://www.strava.com/activities/298620782 . We missed part of the route just before Valkenburg and went back to find it, so the lap is actually shorter with less climbing then in the link. We also started about 10k into the lap. The lap has a lot of cornering and narrow roads. Difficult will be finding spots to eat and taking yourself up to speed after every corner. Reconnaisance is highly recommended.
About the swim: because the river flows I cannot imagine it will be a non wetsuit swim. If it rains in the week before in the Ardennes area in France and Belgium there might even be a strong current.
I hope you liked my first post on this forum!