For ranged weapons
The quality of steel in the 800-1000AD range was generally not good enough to make an arbalest, and designing a longbow able to take much more than a 100lb draw is not easy (see comments for more details). Multi-arm or slat laminated arm crossbows have also been suggested, but are grossly unreliable and not invented until after 1000AD.
That said, even if you could use an arbalest or or multi-arm crossbow, there was one weapon that already existed by 800AD which could outperform either weapon by a large margin: the manuballista. Manuballistas were small enough to be hand-portable but were very front heavy and weighed about 100lb making them impractical to be hand-fired by a person of normal strength. But, with super strength a person could use a manuballista as though it were a hand drawn crossbow. Manuballista used torsion coils instead of tension arms to accelerate their missiles, and as a result had ranges and speeds much greater than any historical bow or crossbow design. Their projectile speeds were more similar to modern fiberglass compound crossbows, and they had massive stopping power from the weight of its missiles. So, while the arbalest and longbow beat out the manuballista in our own history thanks to their portability, the manuballista is a much more powerful weapon than either and the technology can be scaled up to much greater damage potential using the same quality of materials.
For melee weapons
The limitations of steel apply here too, but not nearly as much. When you look at sword fighting manuscripts prior to the introduction of the finery forge, most defensive sword maneuvers were deflective or hilt guards and most strikes were draw cuts. These techniques are designed to limit how much strain you are putting on your blade which suggests that 1x human strength was enough to bend or break these swords if not used wisely. The introduction of better steels in the 1200s came with the introduction of many new block guards and more acute weapon tips for thrusting when steel weapons started to become stronger than humans could reasonably break. We also have plenty of literary records from civilizations all across Europe of wooden handles and spear shafts snapping in combat.
This is all to say the 1x human strength was already pushing the available materials to their limits.
So, a super strong human would not benefit a whole lot from using actual viking weapons, but unlike wooden bows, metal technology could be expanded to make bigger heavier weapons for your super strong humans. So, instead of a typical viking sword which would be about 2-3lb with a blade profile of ~ 3 x 50 x 750 mm, you could give them a much chunkier 1-handed sword with a blade profile more like ~ 7.3 x 120 x 750 mm weighing in at 12-18lb, and still maneuver it with almost the same dexterity.
More strength though does still have its limits here. One limit is that your sword may be 6 times as heavy, but it won't be 6 times as lethal. the thicker you make the blade, the more cut resistance it will have. The edge will also still deform at the same acuity as a normal sword, so you will need to make it duller to survive an impact at full force. Lastly, you may be 6x as strong but your body still has the same inertia; so, fast complex maneuvers with overweight weapons may still throw off your balance.
So yes... a bladed weapon with 6x the cross-section would be more lethal than a normal one, but not by as much as you would think. Instead, I would probably suggest a solid steel mace or war pick instead since they would be less affected by edge limitations and benefit more from greater strength. Basically, picture what a 12-18 lb sledge hammer can do to solid concrete, then imagine what it would do if it could be wielded 1-handed with the dexterity of a ballpein hammer and you are looking at a very devastating weapon.
This is actually where super-strength would be the most helpful. Preindustrial soldiers would often carry up to 70lb of armor pushing their bodies to the limits of what they could carry and fight in. But with 6x strength, your warriors could now carry hundreds of pounds of armor and still remain relatively unencumbered. Furthermore, a really heavy suit of armor could add inertia to your warrior allowing him to wield really heavy weapons without loosing his balance.