Before you get a seeing to from wapping a lot will depend on what your after, what you like and how you are planning to spend the nights. In April I surmise that you are doing the hotel B and B thing. Do you want to travel all the time and stop in different places or stop in one place and explore the local area. France as you correctly put it is massive and there is so much to cater for all tastes. If you want to get any distance then get on the toll roads and crunch the miles. The Vosges is easily reached in a single day if you get an early Chunnel crossing.
If it’s a first trip then I would suggest heading for Albert and spending a few days doing the trenches and the First World War sights. You can easily get across to Belgium to Ypres and some of the Ardennes if you want to. If you want to enjoy the country then keep the mileage down or you’ll spend all day on the motorway and be knackered when you get anywhere. Keep to the d roads and back roads and stop in the villages to enjoy the cafes. Just bear in mind that April in northern France is pretty much like England weather wise, it could be dry but prepare for shite. Riding 400 miles in pouring rain everyday is no fun, it’s a challenge but one I prefer to avoid if possible.
Above all else be aware of the reduced speed limits and the archaic priority a droit which is quite rare now but still in use in rural parts.
Above all, enjoy France as it’s brilliant for riding a motorcycle, nothing feels worse than getting back off the Chunnel in shitey and driving on our roads.