Any airline you fly within Europe will have those same restrictions for Y and slightly better ones for Biz Class.

This is even true if it is the same airline you used to cross the pond. Take, for example, AF on a PHL-CDG-FRA itinerary and you will be allowed the two pieces of checked luggage unless you stop in Paris for a day or so. In that case, you will be allowed only the 20 kgs to FRA.

I can't tell you about Ryan Air specifically, but with the legacy carriers it is a matter of luck. Sometimes they won't pay much attention to the weight limits at check in, other times the very same airline will play hardball and charge you heavily for being overweight.

As far as the one piece of carry on is concerned, I have seen this enforced at check in but not anywhere else. The way to get around it is to take only one bag with you when you check in. (Have your travelling companion check in separately, holding your extra bag. Then you hold his when he goes to check in.)