As far as armour goes, remember that there were nobles who had armour made that was covered with cloth in such a manner that it looked just like normal clothing of the day. We also have doublets that had wooden slats or steel plates inserted into them for protection, etc. Armour wasn't always visible and shining in the sun.
Very true. The term "brigantine", used to describe the type of coat of plates armor also known as a wisby coat, was coined because the wearing of such armor was associated with brigands. This was because it did not look like armor from far away, and it wasn't until one was (too) close that you realised they were in fact armored, and theoretically ready to fight.
This has a lot of interesting implications. We know it was extremely common to carry weapons, particularly outdoors, in the period(s) in question. Full armor, especially plate or mail armor, would be suspicious. Wearing armor which looked like clothing was a way to allay suspicions until it was too late.
The implication to me is that the armor was considered far more of a threat. All of us who have ever sparred are aware how dangerous blossfechten really is, if you are truly unarmored. You are taking an enormous risk, perhaps too much of a risk for one armed person to be willing to attack another. However, if you have armor, the calculus changes considerably, particularly effective armor like a Wisby coat which could actually stop even a good cut or thrust.
One wonders where the helmet might come in...
Speaking of which I think from studying paintings it was also fairly common for people of certain classes to wear armor like Gambeson / Akheton / Jupon, particularly in the summer.
We tend to think, per the fectbuchs, in terms of all or nothing, blossfechten vs harnischfechten, but the reality was probably a lot more often somewhere in between. Even in a moderate state of alarm, like when a feud was going on, people probably didn't walk around in full harness in a city, while going about their business. But something like the armor worn in the account of the Duel of Jarnac (padded coat, mail shirt, gauntlets available if not worn, mail coif probably around neck if not actually on the head) would probably be feasable.
As for mail plus kevlar, I would think that would be awfully heavy, but I haven't seen the latest generation of kevlar. I dont think titanium mail would actually be very effective against cuts since titanium is kind of like aluminum, it's much softer than steel, it just happens to be considered so strong relative to how light it is.
Jeanry