Absolutely it matters.
I would expect up to 10degrees or so higher then a well maintained case
It's not hard to imagine, if you have a medium interfearing with airflow from point A to point B things will get hotter. It's like putting too thick of a filter on your AC it restricts airflow and your house gets HOT!
Having all your cables nicely zipped together, running along sides, etc, air is able to flow through out the case, that includes EXPELLING heat as well as INJESTING new cool air.
Clean it up fellow.
Just google cable managment or youtube different keywords.