teahouse

Are you committed to that major once you select it? Or is it just to show your current interest and doesn't really mean anything?

Any difference in admission chance for the undeclared and declared?

$KingsElite$

If it's an impacted major, you pretty much have to apply for it and get into it to get it. Otherwise, you're not committed to anything. You can apply and get in as a communications major and switch to visuals arts no problem for example (assuming they aren't impacted). But if you want to get into an impacted major, apply for it because there's very little chance you'll get it otherwise. This means, applying for a non impacted major and switching to an impacted one. It doesn't work like that.