The "Great Heathen Army" that attacked the English kingdoms and sacked East Anglia was comprised of both Norse and Danes, but at other times Hibero-Norse kings fought the Danes over interference in their sphere of influence.
Although the term "Norse" can be generically applied to anybody who came from the north, it most properly applies to Norwegian vikings.
The reason the Scandinavians are such saps today is because the tough ones all left to go a-viking. Only the losers stayed home and spawned pathetic weak bloodlines -- Adolphus Rex notwithstanding :)
I was going to go down that path, but then, as you pointed out, the Swedes were still a force in the north uinto the 17th century And also the places the Vikings went to (like England) aren't quite that warrior like any more
it's inevitable - the Persians were horse-riding warriors who took over Elam (modern Fars province) in the 7th century BC and then conquered most of the known world west of the indus 200 years later, yet they were later conquered by Macedonian, Arab and then Turkic peoples