I've never tried the dev rooted image, but I don't think it will grant root to apps. The only root access is via adb shell, AFAIK.
You'll need Magisk to grant root to apps, and you will probably have to flash the normal nvidia recovery image to remove the current root before installing Magisk. You can't/shouldn't have two root methods. See this post in the Magisk support thread. https://forum.xda-developers.com/t/magisk-general-support-discussion.3432382/post-85290505
No one has reported successfully installing Magisk on 8.2.3 in this thread, so if you succeed, please report back. I know it works fine on 8.2.2.
I doubt I will try so I don't get yelled at by my wife lol but I have found some build.prop tweaks that might interest you all..
In a adb shell all I had to do is su root to get permission to change these.
I can't stand the horrible audio quality from the shield, it down mixes everything, and I'm hard of hearing and have to turn subtitles on to understand the words. This helps and makes a big difference in sound quality. You might have to adjust the sound delay settings but worth it imo.
setprop af.fast_downmix 0
setprop af.resampler.quality 255
These two I've been playing with, will report back
setprop audio.hw.passthrough true
setprop audio.is_dolby_formats 1
This command regulates the max frame limit or refreshrate_ui of the AI rendering, I increased it to 121 from 61 and noticed a big difference in motion and quality
Setprop persist.vendor.tegra.deepisp.fps_max 121
I've tried changing the refresh rate but it hasn't worked, thinking I might have to change the hdmi active value but idk