How do older DXA region templates work with "native" regions?

Question

In a DXA 2.0+ setup on Sites 9.0, I believe (in upgrade scenarios) you might still find the older-style region templates, which have a Region (View) Name set in their metadata and possibly a hint in their name (square brackets by convention such as "Teaser [2-column]").

1. Assuming you're using the Sites 9.0 "native" regions feature, are these older-style templates still okay to use?
2. If not used, is it safe to delete the templates meant for regions from Building Blocks > Modules > Core > Editor > Templates?
3. Is there a problem if case editors mix old and new style templates? The older-style region templates still seem to work.

Edit (2019-05-23): I noted the square brackets in Template names are by convention and that the Region Name metadata field actually identifies these older-style region Templates.

Answer 1

1. Older-style templates (i.e. CT with DXA metadata stating what the Region (View) Name is) can still be used, but may be confusing for the user, because the Region information on the CT is ignored; the Region (View) Name is determined by the “native” Region and its Region Schema. If you do a fresh install of the DXA Example Site (and Core Module), you will see that you don’t have several similar CTs which only differ in the Region Name anymore.

2. Yes, if you still have multiple variants of a CT only to distinguish the Region the CP should go in, you can safely delete those variants. Of course, this will only be possible if you are no longer using those CTs on your Pages.

3. You can indeed still use “old-style” CTs. If you use them inside a “native” Region, their Region info will be ignored. However, if you use them on top-level, the Region info in CT metadata will still be respected. So, you can use a mix of “native” and “old-style” Regions on a CM Page. In the Web App, you won’t see a difference between the two types of Regions. You could even combine “old-style” CPs and CPs in a “native” Region in the same Web App Region.

For clarity: note that I’m referring to “old-style” CTs as the ones that have a Region (View) Name in their metadata rather than the ones that have square brackets in their titles. You should use the DXA metadata on your CTs and if you do, the CT title is irrelevant to DXA; the Region name in the CT title is purely informative for the user. However, if your CT doesn’t have DXA metadata, DXA will try to obtain the Region (View) Name from the CT title (inside the square brackets).

Also see DXA docs for help with migrating to “native” (aka “Schema-based”) Regions: https://docs.sdl.com/LiveContent/content/en-US/SDL%20DXA-v11/GUID-182DB837-D05E-4DB7-816B-9D37E159549C