Citus is a completely different animal. This is just vanilla PostgreSQL with a different storage backend. No PostGIS either because just like RDS, no custom native extensions.
The Amazon Aurora database engine is designed to be wire-compatible with PostgreSQL 9.6 and 10, and supports the same set of PostgreSQL extensions that are supported with RDS for PostgreSQL 9.6 and 10, making it easy to move applications between the two engines.
So looks like PostGIS is supported.