Straight to your questions:
1. There is not a single component that can address both requirements as RadSkinManager was designed to facilate the skin management of the Telerik controls suite where as RadFormDecorator provides a nicer look to the regular asp.net controls in an effort to extend the fine look of the Telerik controls to the MS ones.
2. It is difficult without looking at your implementation to say what the cause for those distortions might be - it is most probably a css issue but first we need to inspect your code. That's why I'd ask you to open up a formal support ticket and send a runnable sample that can be debugged on our side.
Thanks for your cooperation.
the Telerik team
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