The squeal could be related to the shims; I've always run them in my Sumitomo calipers, and never had issues.
It could also be incompatibility between the old pad material (layer on the rotors) & the new pads; this is very common.
Some pads will refuse to work with the layer of material left on the rotor from the previous pads; it's always a good policy to give a light skim when changing from one pad material to another, unless you KNOW they are compatible.
Overheating pads in the "Bed In" phase can cause the bonding material to be drawn to the surface; this effectively glazes the pad.
Sometimes scuffing can save them, sometimes they are unsalvageable.
People are tempted to get new pads very hot, by doing heaps of very high speed stops, because they are going to use them hard.
Often, the temps required to set the bonding material are quite low.
The Remsa's have a reputation for not being squealy, nor are they very hard on rotors, but they are dusty. I'll take dust over squeal any day.
Hopefully it's a simple fix.