I want to build a portfolio website where the visitor can pick which kind of layout he wants to view it in.
But keep that choice trough-out the whole site and show up in the url
Similar to language switching. (www.portfolio.com/layout1/project)
I thought about abusing that system and create fake languages but there must be a better way of doing this.
Is it also possible to link this to an other template, or css?
I think there are different ways to achieve this, you could use URL parameters (or URL slugs, like you suggested) or cookies.
I probably wouldn’t use different templates, but snippets or, if the different stylesheet is enough, load another CSS file depending on slug/parameter.