How to get SD-card write access on Honor 6x with Android 7.0?

My phone is a Huawei Honor 6x, using Android 7.0 (Nougat). EMUI version 5.04. I want my music apps to have write access to my music folders on my external micro SD-card. I understand that this might only be possible if **all** my apps have access to **all** my folders on the card. I would prefer to do this without rooting my phone, but if that is not possible, then please recommend alternate methods. **What I've already done**: Install *Fx File Explorer* on my phone, but this only creates write permissions for itself, not for other apps. That seems plausible of course, but that was not as I was told. Questions: 1. How do I get write access to folders on my external micro SD-card, without rooting? 2. If it is not possible to get access without rooting, what is the best method to root for my type of phone and OS? 3. Can I root my my type of phone and OS **without** or **with** unlocking the bootloader? 4. Is formatting the SD card as internal storage a better option? Or do I need to root my phone to do that anyway?