The token container of RadAutoCompleteBox is a Div element which does not have a specified height therefore when the specified width of the control is reached the tokens are moved to the next line. You may specify certain height of the Div element but the input element in which the user is allowed to type will still move to the next line when the end (width) of the control is reached. It is just that the control is not designed to be customized like that.
As for customizing the tokens, this is again not supported by RadAutCompleteBox although we are contemplating on it. It seems like a good feature to be added to the control -- if it turns out that it is achievable to develop such a feature you may see it in the future versions of RadAutoCompleteBox.
the Telerik team
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