This app was mentioned in 11 comments, with an average of 1.73 upvotes
You can use the theme editor app to change your font system wide. I have used it on EMUI 5, not 8. But I think it should work.
I'm in EMUI5 and I've used the EMUI Theme Editor to combine the "Genius" theme from the Huawei theme store with this theme's (XDA link) navbar.
http://forum.xda-developers.com/p9/themes There's a bunch of themes on here. Also this app allows you to edit certain parts of a theme. I cannot remember if it allows you to edit the notification bar colour.
Not that I'm aware of. I know that themes for the P9 also work for Honor 8. You could also try a third party theme editor that should allow you to change the background of the Notification Panel if you wanted to try that out. EMUI Theme Editor
Download Theme Editor and edit any non-built-in Huawei theme
Pick a Theme ➡ Start ➡ Font ➡ Pick either one of these ➡ Done ➡ Back ➡ Next ➡ Choose either
After you save the theme (file ends with .hwt), move the file to /storage/emulated/0/HWThemes and then restart the built in theme app and you'll find your theme there.
I use it to also edit system app icons.
You can make fonts using these apps, and you can also get new fonts from them!
https://play.google.com/store/apps/details?id=com.mixapplications.themeeditor
This works just fine for me.
Maybe try this app? It says it can change EMUI icons
https://play.google.com/store/apps/details?id=com.mixapplications.themeeditor
Use this
https://play.google.com/store/apps/details?id=com.mixapplications.themeeditor
You should be able to just add a font but leave everything else stock.