How can I add timestamp into my table when I use Write-DbaDbTableData?
When I was arranging a similar setup in the past, I did the following:

Use -AutoCreateTable to generate the basic schema for any commands I wanted to write to the database
Modify the tables to use better data types + added a column with a default GETDATE() value
Pipe any results into the newly modified tables.

This is also helpful since any updates to the command output will break due to schema differences and force you to adjust the code and table as needed.