I'm having a little problem here. So I changed the group of a folder including subfolders via chgrp -R groupname and it works all fine but I'm using transmission and pyload to download files into those folders and they both write the files as root in there.
Can I somehow change the default group/user for the specific folder so that it also includes new folders/files?
First of all, it's not recommended to run pyload as root. You better take a user which has full read/write permissions on the pyload home folder as well as the download folder.
Second, inside the pyLoad-WebUI, you can choose under Settings->Menu->Permissions how pyload should handle file-permissions.