Both. I'm a big fan of using filters to move them around. I need a zero inbox else I'm driven mad.

Both. But if need to choose one of them - labels.

Gmail created tabs. All outdated emails I just delete

Folders and subfolders. Also creating alot of rules to more efficiently manage emails along the same theme...

I need to use more filters/tags - but I like to keep it stupid simple.

Folders > labels

Labels

Folders are like the Bermuda Triangle