A common problem people have been reporting is the inability to reformat an APFS drive as something other than APFS. It appears in Disk Utility that you can only erase a disk and keep it as APFS. However, a simple switch in Disk Utility is preventing you from selecting the device rather than the volume. Once you select the volume, you can reformat however you like.
Here's a question that's been asked a lot recently all over the internet. How do you reformat a drive that is formatted APFS? APFS is the current way to format Mac drives. But if you need to reformat it, say as the older Mac format or maybe a cross platform format with Windows, it seems like once you format something like this thumb drive at APFS you can't reformat it as anything else. If I click Erase here you see that the only format options I get are APFS. But, in fact, it's a completely different problem and a very simple one to solve.
You see in Mac OS Mojave disk utility has two view modes. One where it shows only the volumes and another that Shows All Devices. So I switch to Show Devices. Now you can see that I'm actually selecting the Thumb Drive Volume inside of the one container for this actual physical device. So before we had, say, a physical device for the drive and then you had volumes. Now with APFS you've got Device, Container, and then Volumes under that.
Now when you have have the Volume selected, the volume is APFS. If you go into Erase it you can only erase it as an APFS. But if you move up the chain you see that you can change the container to be something else. Or probably what you want to do is select the Device and the result might be the same. Now you can actually change it to whatever you want.
So all you need to do is switch to Show All Devices. Then select the actual drive itself. Click Erase and now you can get to whatever you want for a format.