I think, most times its better to have seperate templates for different page-layouts. For parts which are the same on both layouts you can use chunks and
put them in your templates for example like this.
{{doctype}}
<html>
{{head}}
<body>
{{header}}
<div id="pagecontent">
{{left_column}}
{{middle_column_A}}
{{right_column}}
</div>
{{footer}}
</body>
</html>
another way or in combination you can go is create checkbox-TVs with input-option-values as:
show middle column A=={{middle_column_A}}||show middle column B=={{middle_column_B}}||show right column=={{right_column}}
and you can add textarea-tvs for parts, which may change from parent to parent and make use of @INHERIT-Binding as default-value.
if you want to change only the width of one column you can create a radio-tv for different CSS-classes with input-option-values:
or if you have two different templates use the template-id for changing CSS-classnames. For example class="middle_[*template*]".
..................
