In Denmark we usually have coalition governments, and when they are constituted you can see who’s important and who’s not from the ministries they are given.
Some ministries are more important - Finance, Justice, Foreign Affairs - and some are less important.
But which commission posts are the most important and powerful? I want to take a more active interest in EU politics, but that requires me to know what to look for :D
I think an important one to look out for is who are the vice presidents. Those (and their posts) are probably the more important ones.
Other important people are the Parliament president and the president of the Council (roughly equivalent to a country’s senate). Understanding the three bodies of Commission, Parliament, and Council is the lowest hanging fruit towards understanding the EU in general.