Use different placeholders when the allowed components are different. In the placeholder settings, you can set for a placeholders the allowed renderings.

There are basically to approaches.

1. use 2 different Layouts with different placeholders.

2. 1 Layout, with a placeholder where you can place only your page renderings. where the page rendering is just a normal rendering with less html but with 1 or more placeholders.

Then you have a rendering preLogin with placeholder prelogin and a rendering afterlogin with placeholder afterlogin. In the placeholders setting from prelogin and afterlogin you define the allowed components, renderings.

Of course you can have more placeholders like header and footer.

Use different placeholders when the allowed components are different. In the placeholder settings, you can set for a placeholders the allowed renderings.

There are basically two approaches.

1. use 2 different Layouts with different placeholders.

2. 1 Layout, with a placeholder where you can place only your page renderings. where the page rendering is just a normal rendering with less html but with 1 or more placeholders.

Then you have a rendering preLogin with placeholder prelogin and a rendering afterlogin with placeholder afterlogin. In the placeholders setting from prelogin and afterlogin you define the allowed components, renderings.

Of course you can have more placeholders like header and footer.