I have a Win10 BootCamp partition, and a High Sierra partition. The High Sierra partition has some dodgy drivers and system extensions from old hardware and software I’m not using anymore, and I want to just clear it all out.
I also want to roll forward to Mojave.
If I nuke & pave the High Sierra/Mojave partition, I wouldn’t think that would affect the BootCamp stuff - but I’m wondering if anybody has first-hand experience with this.
Any advice?
I tired this a while back and was very nervous. I ended up using some software called Winclone for just this purpose. It allows you to backup your Bootcamp partition to a file. Then, I nuked the entire drive (so I don’t have experience just blowing away the macOS partition like you are asking), reinstalled macOS, and used Disk Utility to adjust the drive size and restore the Winclone backup. Hope this helps.
Update - after taking a ton of backups, I was able to nuke the Mac partition and replace it without affecting the Windows partition.
Started with High Sierra and Windows 10.
Upgraded High Sierra in-place to Mojave.
Then went into Disk Utility, erased the Mojave partition, and reinstalled from scratch.
After install, I could still dual-boot with my Windows 10. No issues. 
Thanks for reporting back. I wasn’t brave enough to try that without a backup.