Hard water is a pain , it’s why I prefer creams, water here is so hard that my scuttle showed limescale after a couple of days (on the reservoir edge) of having water in for 20 mins or so ..
In respect of original questions, I honestly think that sample packs are a pain, the only way I’ve found it to work is like a ‘knock out competition‘ (no royal paedos required) and to dismiss and forget anything that I don’t like.
You quickly find that once you are used to the razor, the differences between your favourite blades are fairly miniscule, it then comes down to costs