format new drive APFS

What are the error messages?

See if anything about your hardware is mentioned in the APFS section via the release notes.

http://adcdownload.apple.com/Documentation/Beta_Release_Notes_Jun_21_2017/macOS_10.13_beta_2_Release_Notes.pdf

I think your problem is due to you trying to convert your internal drive via an external drive, I'm not sure why but that seems to be a regular problem.

At present APFS seems to only really be okay when it's installed on an internal drive, I'd suggest you just install 10.13 on your internal drive and tick to box for conversion to APFS.

Do you know if the App Disk Utility work to convert APFS, because now with JDL case I am wondering.

I convert my 2 internal partitions in APFS in recovery mode (to convert the boot partition that was not allow by the Beta installer due to HDD drive).

Then in normal mode, I try to use Disk Utility to convert my external USB drive (normal HDD drive, not SSD), and it failed (com.apple.StorageKit erreur 118).

As I don't really need to convert it, I will wait for another build and see how it evolve.

I am assume the reasson why you can at the moment on an external drive would be for the same reason they turned off Time Machine.

Switching to an entirely different formatt there are bound to be issues supporting external Hard-drives espically since up til now manufactors have been making their External Drives to Support Apple's now old format. So it is to be expected that there will be issues with external Drives to an extent.

either Apple will need to figure something out to support the Drives or a firmware update would be needed on those external drives

As far as I can tell, if you have an SSD and install 10.13 beta formatted to APFS you're able to convert an external drive to APFS too, but there have been a lot of reported problems with this so my thinking is that leaving conventional HDD formatted to HFS is the safest option, if you want an APFS external drive it will be best to have an SSD as your external drive.

Internal 1TB Fusion drives seem to work fine too but not drives as large as 3TB.

I don't think Apple will ever support APFS formatting for conventional HDD's, it will only ever support APFS on SSD'S or Fusion drives.

TimeMachine worked fine on external drives formatted to HFS up until update 1 then a problem was noticed so I don't think there will be an ongoing problem with running TimeMachine once this recent problem is addressed.

Apple has stated that external drives used for TimeMachine must be formatted to HFS not APFS.

If you want a stable external drive formatted to APFS I think your only option with be an SSD, which are coming down in price and increasing in capacity, I think Apple looks at conventional HDD's as old tech now and they won't invest much getting conventional drives working with their new file system.