Unicode comment on Postgres vs Sql Server

I am familiar with MS Sql Server & just started using Postgres.
For storing Unicode, Sql Server uses nvarchar/char for unicode, and uses
char/varchar for ASCII.
Postgres has this encoding setting at the database level.

I am using UTF8 Unicode for most of my data, but there is some data that I
know for sure will be ASCII. However, this is also stored as UTF8, using up
more space.

At first sight, it looks like the the more granular level design is better.
Any comments? If you agree, does it make sense to add this as a new datatype
to Postgres?

Thanks