The ease of removing/fitting Marathon Plus tyres does to some extent depend on the particular rim with some rims being easier than others.
That youtube video above is now a good few years old and the guy doing the tyre fitting is 'Colin', a renowned wheel builder who used to work for Spa Cycles (now retired - and known as Colin531 on the Cycling UK forum).
I was forced to follow his guidance more than once but I got so 'hissed' off at the time spent to get the tyres off and back on again, especially on a cold, damp winter's day, that I gave all my M+ tyres away.
Before you ask as to what I used as a replacement, I am not an expert in these things and there are so many factors to consider - my general criteria is price vs performance and having a reasonable resistance to punctures as I'm OK with fixing such things out on a ride.
As for wet weather performance, I really can't say as I'm mostly a dry weather rider now I'm retired but as has been said already, avoiding metal covers, patches of muddy roads, potential icy spots at the bottom of hills (frost rolls down hill and collects at the lower points) and so own, lead me to exercise careful road craft especially as I now no longer bounce of tarmac in the 'minimal harm' way that I used to