[ZTE Axon 7 Questions & Answers] Darkcrafter3@gmail.com:
***UPDATE***

Thanks to reply, I have now successfully done everything I set out to do, and created follow-up guide!

You can find it HERE

Original Post below:

Hello Everyone!

I'd like to start off saying I used to have a Nexus 4, with TWRP and Lollipop-based CyanogenMod. I was able to install this all by myself, and keep both TWRP and the ROM updated. I also flashed custom radio to unlock the LTE capability on that phone. My tool of choice to help customize the phone was Nexus Root toolkit.

I was able to follow guides posted long ago on these forums, to do what I wanted with the Nexus 4 back in 2013/2014, but it seems I'm not so capable these days. I've hit such a roadblock with lack of root and constant stutters/slowdowns with everyday use on my current device, the Axon 7, that I must get away from the stock software. I heard it was not so easy with other devices, and while a few devs have posted wonderful guides for users, it's just not enough for a true beginner like me. From skimming guides posted, it seems like devs already expect you to have installed custom recovery, or unlocked bootloader. Then when I try to do these things, so I can move onto custom ROM, it seems the guides are out of date or just not step-by-step enough for me to use, and I don't want to take a risk and brick my device trying things that I'm not sure about. I'm a power user through and through, but not so up-to-date or knowledgeable enough to be able to follow the guides already on the forums. Consider me 1 out of 5 on tech level for Android software.

Here's the model/software already on my device: Stock everything, from bootloader and recovery, to ROM.

Model: A2017U, Nougat 7.0 on B15 ROM

What I still need clarification on:

with my device already running on nougat, do I need to install the nougat universal bootloader/radio I saw in earlier guides?

will LineageOS have any downgrades in regard to audio quality, on either the headphone output or speakers?

will my ROM of choice have Daydream VR support? if not what would be needed?

this is not a big deal, but do I need a special app or entire custom ROM if I'm interested in a temporary unroot to use apps like Android Pay?

Here's what I want on my device: TWRP, LineageOS with root.

If anyone, expert users and devs alike, could reply with current known-good info about the following, I and a lot of other users would be eternally grateful:

unlocking the bootloader, installing TWRP, and LineageOS, in a stupidly long but simple step-by-step process.

Quick follow-up info:

What I can do so far: download current LineageOS nightly, correct version of root .zip, and TWRP from official websites

NO, I'm not good with using ADB on Windows to get things done. I had to ask a friend to help me install it on windows, the guide he sent was much easier than the one i was using, and he still had to walk me through how to use it once installed to help me unlock bootloader/root on another device, Zenphone Zoom if anyone is interested.

PLEASE, don't link me to other guides for any part of this process, if the steps are thorough and relevant, please copy here, of course with all due credit given to original poster.

Feel free to let me know if more info about my knowledge level or device is needed to help you work on my request.

Thanks for reading, here's to several years more of everyone enjoying this wonderful device!