How to create loging page as standard page type

It looks like you’ve asked a very similar question at How to over write login page template. Are you trying to do two different approaches on two different projects, or is this essentially a duplicate thread?

In either case, this isn’t something that’s supported out of the box with Silverstripe CMS. It’s possible but unlikely that there’s a module for this - most likely you’ll need to create a bespoke solution. It’s not a very common use case.