No telling or confirmation whether deleted files have been written over
Due to the nature of how TRIM works, deleted files do not immediately get overwritten. It just earmarkes deleted files to be overwritten first when new files are created or as existing files grow.
For just a few dollars one can purchase Cindori's flagship product Disk Sensei. There's also a simple command line argument one can issue. Read more on howtogeek.com for the details.