As for boats, the Viking age has been connected with acquiring sail technology, not so much with boats as such (which have existed for a long time, the rock carvings you linked to show depictions of boat designs which have actually been found in archeological digs, and that indicates that older, different carvings are also true and that boats were used for long distance trade and expeditions a millenium or two, at least, before the Vikings).
If the appearance of efficient sail technology really coincided with the beginning of Viking raids is still in the open I believe.
Then the media will turn around and print something absolutely outlandish based on a total hypothesis, just because it attracts clicks.
This site suggests "Germanic groups such as the Saxons, Franks, and Frisians". That seems like the more parsimonious explanation.
More... than what? What do you think Vikings are?
https://upload.wikimedia.org/wikipedia/commons/0/0b/Europe_a...
INTPenis is mentioning Angles and Jutes because they were in present day Denmark (and England). You might ask what the cultural difference is, from Vikings, and I'd flounder. Vikings spoke Old Norse, a germanic language related to whatever the other tribes spoke (um, West Germanic, such as Old Frankish). They believed in gods related to the gods of these other tribes and used similar runes.
Well, the Saxons famously had Saxes: https://en.wikipedia.org/wiki/Seax
If you want to say this is an arbitrary modern set of categories ... I guess the Romans are responsible for the categorization really, by writing down tribe names such as Frisii.