Does the default tax apply to cloned and converted transactions?

No, the default tax does not apply to cloned records or to transactions converted from one document type to another. In both cases the records carry the tax from their original source:

• Cloned records: carry the tax from the original record they were cloned from.
• Converted transactions (such as Sales Order → Invoice, Estimate → Invoice, or Purchase Order → Purchase Invoice): carry the tax from the source document.

The default tax only applies to transactions created from scratch.