If riding in rural France, well worth 5 mins familiarizing yourself with the local signs (2 of each) that let you know who has priority at junctions / roundabouts.
Ref filtering, I found the Dutch incredibly helpful, the Germans incredibly unhelpful. Presume (don’t know) legality of filtering is different in Holland/Germany. Also for those tempted to undertake, Germans hate it and will definitely react, try and prevent this. Presume it is illegal there given their strong reactions.
On the spot fines, if you like to risk it, make sure you have the cash as fines can easily be over the 300 euros you can get from an ATM. And be prepared for fines in the post from fixed cameras. I checked the colours of cameras on Google, but there is no uniformity here. Pain in the arse if you are touring.