Can the default case view template (Summary Panel,case work area, utilities panels) be changed in cosmos be changed?

As per point 4 in this article it shouldn't be customized, but there is a new template available from Pega 8.4 for the case view( template name:wide case page UI template) as per this video.

So this means the cosmos default case view template be customized? Will it create any issues?

Thanks in advance.