A Delta table combines data files with a transaction log. The log records which files belong to each version, so readers see a consistent table while writes commit. CREATE TABLE with an explicit schema makes an empty table. CREATE TABLE AS SELECT, often called CTAS, writes the query result and derives its columns.
In Unity Catalog, a name has catalog, schema and table parts. Use a new silver table for cleaned data instead of changing the bronze feed. INSERT appends rows; CREATE OR REPLACE replaces the table's current contents. Those operations solve different problems. This browser records versions in its session to practice the distinction. It doesn't create cloud files. Always inspect the resulting rows after a write, because a successful command can still write the wrong source or replace data you meant to keep.