How to Make Section Templates Render Correctly

I’m having all sorts of issues with section templates. They seem to render by default as ‘blocks’, which by default have 100% width. You can set it to ‘render without wrapper’, but this only affects the front-end. It’s making a mess of the display in the editor.

I’m using templates for a search box and a left sidebar. The search box template is nested inside the left sidebar template (as well as being used in a couple of other places on the site). My left sidebar wants to be ‘width: 100%’ by default, so it is stretching much wider than it should.

Is there a preferred way of setting this up so that the template is just inserted as it has been created, without the wrapper in the front or back end, or with the wrapper in such a way that it doesn’t try to expand to 100%?

So just after posting this I realised that setting the width on the template as auto basically solved this problem!