I was finally able to get the two henchman I edited to appear by naming them KSHenchMan65 and KSHenchMan66. I wasn't able to get them to appear without changing the number to make it a new henchman. Overwriting existing henchman just wouldn't work for me.

Something to note: you can load edited and new henchman into the Main mod, and thus get your custom henchman in vanilla saves.

Editing lsx files with Notepad++ didn't give me any issues either.