Is possible to debug Eclipse RCP Product? If yes, how do I do that? I found arguments like
-vmargs -Xdebug -Xnoagent -Xrunjdwp:transport=dt_socket,address=8000,server=y,suspend=n
but no idea where put it and is it enough to debug? Is it should be in VM Arguments (file *.product tab Launching)?
Start the application as you described, by adding the -X parameters.
Create a new Remote Java Applicaiton in eclipse like

the Port has to be the same, you used in
the project you select, has to contain the class you want to debug. You also can add all projects of your worksapce to be sure, that you can debug any of them.
You can also check debugging-java-applets-in-eclipse