Despite being called the United States, America is not a confederation but a single federal state. The Southern states which tried to leave the union in events leading up to the civil war attempted to create a "Confederate States of America". The name makes it seem like a confederation, not a more unified federal state.
Did they really intend to form a more loose type of union than the United States? Why?
This is mainly a misunderstanding of the term 'Confederate'. The simple definition is "joined by agreement or treaty'. It's a synonym of allied, alliance, United, union and several others.
The Confederate Constitution is mainly a copy of the United States constitution with some changes. You can read it here
the Confederate States could be as centralized or decentralized as the United States through the interpretation of law.
The Confederate Government did struggle with State governments over manpower and resources throughout the war but that has more to do with the Confederate Government being a newly established authority dealing with established and entrenched governors.
The Confederate Government levied taxes, raised troops, in fact it enacted the first conscription an American republic would enforce, it built infrastructure, railways and factories
All in all, the Confederate States of America was a centralized federal power comparable to the United States of the same time period.