I’m currently mindblown at one of the programs publicly available for download in the software, which is a NEC PC-8801 emulator... I peeked at the BASIC code and it does indeed appear to be emulating a Z80 and it even includes support for loading real BIOS dumps and floppy images seemingly.

I can’t find much information about the software online but I think it was developed for one of the competitions and I’d highly recommend checking it out if you decide to purchase SmileBASIC 4.