Mojave on Mac OS Extended?
I would suggest putting on APFS as you have SSD drive even the current situation will not hamper anything but you can use the optimal resource as required when you put on APFS. 


APFS, or Apple File System, is the default file system for solid-state drives and flash memory in 2017’s macOS High Sierra.
If you’ve got a mechanical hard drive, and you intend to use it only with Macs, it’s probably best to stick with Mac OS Extended. And any drive that needs to work with older Macs, running El Capitan or earlier, should absolutely be formatted with Mac OS Extended because APFS is not compatible with those computers.