RadPageLayout is not 100% wide on bigger resolutions by design. You can override the behaviour quite easily.
On your other question, about the height -- yes it's possible to achieve 100% height, although requiring some manual CSS. It will not work automatically, because there are many cases in which such automatic sizing will break things, rather than help.
To further assist you, we'll need at least a mockup of your design so we can say if the PageLayout is the right tool for the job.
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