Hey @TonyBear,
Yes, global blocks can work too. It is just that there are cases that the resulting CSS codes for global blocks will have issues later if there are several other blocks on the page.
Since you are using the custom layout, Just use the elements inside the custom layout. You can also assign your custom layout to other pages as well. You may also use conditions for the sidebar so that you can select which pages you want it to show or hide to minimize the number of custom layout. For example, if the layout of the blog index, archive pages and search results are the same, I would probably use one custom layout even if they will have a different sidebars. I can throw in 3 sidebar structure set up in that custom layout and just use conditions so that I can display different sidebars. This will make my editing easier since I will only be editing one custom layout and I can edit the sidebars as well in the builder without going back and forth to another builder unlike when using the global blocks.
Hope this makes sense.