I would not waste my money on Tech Tool Pro. Yes, it has a utility it claims can repair an APFS volume, but it does not really do anything and the rest of the Tech Tool Pro suite I personally find is very subpar. TechTool has never been that great of a utility suite (it was the third one on our list even back in the PPC days) and the last time I tried it a few years ago it was no better and no more useful. Anything included within it can be done much better with other individual apps. Apple has not released the necessary APFS documentation so any utilities out there are not going to be much more than what First Aid is. If you cannot repair an APFS while using First Aid from Internet Recovery Mode or from a bootable macOS USB installer, then save your money and backup your computer before erasing the whole drive and restoring from the backup.
You should always have frequent and regular backups of your computer and all external media (including the cloud) which contains important & unique data.