[noggin]

is odroid n2+ still the recommended device to get over any new devices that are out there?

From what I been reading these android devices still got some issue with audio - atmos dropout..
How big of an issue is this for most people?

https://forum.kodi.tv/showthread.php?tid=332180
WARNING ! - All hardware running Kodi will have issues with Atmos audio dropouts with high bitrate Atmos Disney (click) & Atmos audio (click) Bluray Rips - the exception is Android platforms like the Nvidia Shield (probably the 2016 Mi Box too) that has a fix in the Android OS - ExoPlayer (click) - AND on those platforms you have to use Plex (click) for playback.

Is apple 4k 2021 still the best media player for 4k HEVC 10 bit HDR
without any sort of issues e.g. atmos dropout or whatever issues..

The big downside is you can't install Kodi on apple TV 4k 2021 unless there is a jailbreak for it.

Apple TV 4K won't do Dolby True HD + Atmos - it only does Dolby Digital Plus with Atmos.  The ATV 4K has no option for HD Audio passthrough/bitstream - just decode to LPCM 5.1/7.1 (lossless for 48k/24 content but no metadata is sent to your AVR). It is definitely the best player I've found for DRM streaming services though - proper frame rate switching with both Dolby Vision and Dolby Atmos (i.e. DD+ with Atmos) support for Netflix, Prime, Disney+ and Apple TV+.  MrMC does a reasonable job for my local media playback (that I would use Kodi for on other platforms)

CoreElec on AMLogic S905X3 and S922X platforms like the ODroid C4 and N2 (I don't have an N2+) is good for pure Kodi stuff.

The Shield TV kind of does both - but it's DRM performance isn't as good (no dynamic frame rate switching on DRM services - just a kludgey workaround) as the ATV 4K.

(I have all four - my ATV4K v2 is my daily driver for Netflix/Prime/Disney+/ATV+, my C4 is currently in use a lot for Kodi replay of local media and Live/Recorded TV from TV Headend)