For Literata, I would recommend
Literata Book. I have both 'regular' Literata and Literata Book on my Kobo. I cannot remember the differences now, but I prefer Literata Book.
You do have to patch the firmware to get advanced font controls on sideloaded fonts, and I do use the patches. But to be honest, I never actually use the advanced options once they are enabled
Try adding sideloaded fonts without the patch if you don't want to mess with it. Odds are, you will be happy with it as is.