I have done tech support officially and unofficially on Mac computers for years. I still have most of the tools necessary to take apart and fix Macs. My two go-to Apps for diagnosing macOS software and hardware problems are DiskWarrior by Alsoft and Drive Genius by Prosoft Engineering. They are great Apps, but they are not macOS High Sierra APFS ready.
Alsoft says DiskWarrior 5 will run on a APFS volume, but it does not recognize APFS volumes for repairs as yet. Here is the warning DW gives you when you boot it up:
I can confirm this. I have DiskWarrior 5 running on my iMac APFS formatted hard drive. It opens fine and will work to repair a HFS+ formatted drive. It sees my external Clone drive which is HFS+, but does not see any other external APFS formatted drives. They are promising that a future release of DW will be APFS ready soon. I sure hope so because I use this App fairly often to troubleshoot my machines and others as well.
Prosoft took this whole thing a step further. Drive Genius can be installed on a APFS drive. However, when I ran it for the first time after upgrading my iMac to High Sierra APFS it downloaded a new version that essentially disables DG on APFS machines. When you boot up DG it gives you this warning:
The DG App will not even boot up!
This is not like it is the end of the world. Both of these applications have been around on the Mac for years. They are both high quality Apps, very reliable. It is just going to take some time until they are updated to work with APFS volumes.
Apparently, part of the problem is Apple has not released full documentation of the APFS file format. Really? Hopefully, Apple will release this documentation soon so the rest of us can get on with our tech lives!!
If you are into the tech thing then you probably already use DiskWarrior and/or Drive Genius. Be patient, they will be updated soon enough. If you do not have either of these Apps, but would like to do a little more tech support on your Mac, I highly recommend either of them, or both if you can afford it.