This tool is free for anyone to use (even though some of you might be my competition ( ಠ_ಠ) ), no ads, no email popups, no tracking cookies.
I can't say for sure if it's better for Etsy SEO to use all available characters in your tags or if it's better to keep phrases intact. I've tested it in my own shop (Top 1% Etsy Seller without selling masks) but there are simply too many variables and too many unknowns.
From reading Etsy's Guide to Search, you shouldn't use a word more than once in your tags and etsy's search algorithm will put words from separate tags together to match a query.
But since Etsy doesn't share everything about how the algorithm works, I make no guarantees or promises as to the effectiveness of this tool. Use at your own risk, not a doctor, your mileage may vary, not financial advice and so on.
The term 'Etsy' is a trademark of Etsy, Inc. This application is not endorsed or certified by Etsy, Inc.