Is there a claim on the English crown? Does Denmark start in a strong position as it was during this time?
Yes, Denmark has a claim on England from start. And it is inherited by all his gazillion children as well.
I have read Captain Gars' Sweden adventure that didn't go anywhere more than a few words.
Did you actually read both of them? Because the claim on England is mentioned in the second one. And at the end of it I had conquered large parts of the Baltic tribes, taken the English crown as well as set myself up for taking over all of Sweden (which I later did). So Denmark starts of pretty strong. It also has elective succession which I personally like as it allows me to choose my heir. The biggest pain starting as Denmark is that you have something like 13 children that all wants educations, marriages, land and titles...