You're right about room temp butter and handling it less. That's the secret to keeping the crust tender. When butter is rock hard, you have to manhandle the dough to mix it, and that makes too much gluten. Soft butter blends in fast so you can stop mixing sooner. I take it further by using my hands to gently press the dough together instead of kneading. Then I let it rest in the fridge so the butter firms up without toughening the crust. It turns out so flaky it almost shatters when you cut it.