Is there a more performant alternative than overriding template files? I've got to get rid of a lot of unnecessary markup in a view. In general, I accomplish that by overriding the template files in my theme, but this time the view is really huge and performance is going down. So I wondered, if there's a more performant way to reduce markup? When altering the markup of a node, than preprocess functions are faster then overriding template files, is there an analogical mechanism for views?

Edit 1: Sure, the reason for the weak performance is not the overriding of template files on the first place, but if I can optimize a bit there, I'll have to do that. In addition I regularily get into trouble by disabling markup in views UI itself: disableing row-styles for example is ignored when I use an Omega subtheme …

Edit 2: I am aware of the possibilities inside the Views UI; What I am looking for is a manual way with fine control.
You can eliminate unnecessary markup through the Views UI. 

When you add a field, hidden under Style Settings, they always have this default unnecessary checkmark 



Also, you can remove more markup here



and here