Safely Wipe Mac OS SSD In order to sell my Mac (running High Sierra), I would like to know if there is an absolutely secure way of wiping all data preventing any recovery possibilities from the next owner?

I've read many articles or blog entries stating that the usual "secure deletion" tools do not really work for SSD disks.
Thats true. SSDs work a little different than the usual HDDs. A program that overwrites the memory multiple times does more harm than good on SSDs. You kinda have to trust apple that their ERASE function actually securely removes any information. There are also certain SSD erasing tools, but it comes to trusting them once again. If you don't want to trust them I suggest you to encrypt your SSD and then erase it. You can use FileVault (or third party encryption software) and after setting it up simply use erase. This method is very safe and as long as you don't try to hide secrets from the government you should be fine thehe.

In SSDs you first have to erase the target area before you can write to it compared to HDDs. The Flash memory is divided into blocks, those are again devided into pages. You can directly write into an empty page. However if you want to delete, it can only be a whole block. SSDs tend to wear out after extensive use, so it's generally a bad idea to write unnecessary ammount of times. When writing a sentence the SSD's controller will read the page, then write a new page (with the sentence mentioned earlier) to another location. Old page will be marked as empty. The old page number will be assigned to the new page. If you overwrite the SSD multiple times, the reserve space is not gonna be touched, hence leftover information could be investigated by an attacker. Once again this comes down to trusting the vendor that provides the erasing functionality. Encrypting the whole disk eliminates this problem.