What stats to look for in a surge protector, how to compare them and what are recommended some European surge protector brands (and models)?
Honestly, your search is a waste of time. Surge protection is something which has to be done inside the mains filter of the actual device, and has to match the device's power ratings. These surge ratings you have there for the APC UPS are useless information about the properties of its mains filter.

It's like telling someone your car has a 5.7l motor.

For power strips, these ratings are especially useless because they don't have enough space to fit decent filter coils in it. A coil would indeed protect all the devices behind it against surges it because it's in series with the live and neutral wires. The "surge protection" these power strips offer in contrary is simply a varistor along with some X- and Y- caps filter. They leave out the filter coil because a 10A one with enough inductivity to help won't fit into the power strip. Yes, that arrangement eats up some small surges. But not for the devices behind it (it's parallel to the mains, so there is no behind) but for all devices in your house.

It's like telling someone your other car even has a 6.1l motor, because you hauled a scrapped one into the trunk.

So, while these ratings are technically correct, they are of no practical use.



Buy devices with decent power supplies. Cheap supplies cost as a little as 1€ in whole sale – so you know they are crap. A rule of thumb: The power supply should cost as much as the electronics behind it.