I'm using a lower end unit Himedia H8 Plus and updated to new firmware. I don't see is there any noticeable the occasional loss of synch. Even playing a 4K 60fps 5.1ch vid. Is very smooth. I believed Q5pro does better.

i am quite sure u do not know what is meant by that bolded sentence.
that sentence refers to playback with KODI player, as in the app KODI.
that, is the heartache of many boxes using kodi - pls read kodi thread.
becos many people like to playback their hdd collections with KODI player - for kodi's artwork.
some like playback with other players like MX or VLC.
take note some boxes do not come with native player, i.e. a player where u play direct clean and simple, no need another app player.
himedia used to be a pure media player co., every box they make comes with their own himedia player.
Q5/Q10 pro native player is a powerful one, with imprex engine2, can do extras like HDR, dolby vision, DTSX, online subtitle download, picture quality parameters adjustment/tuning - not found in most other players.

so, that sentence refers to playback with kodi app as it is. the last bit about wrapper means if u insist on playing back with kodi player, himedia's solution is to use the wrapper, an app which "wraps" the stream from kodi, bypass it and play thru the native player. this wrapper, for now, works fine if u playback with kodi but does not work with regular kodi online streaming, something that needs to be fixed by a new firmware, not done yet.

i do not like local playback with kodi, prefer playback direct with native player. have used q10pro for 3 months now, have hv not seen a single file in my collection that does not play correctly.

i do not know what files u have in yr collection, but i have banyak terabytes ... all sorts... incl 50, 66gb, 4k, hevc, 10bit, mkv, m2ts, iso, whatever...
afaik, the native player in q5pro is the same with q10pro.

there are 2 diff between the two - q5pro is 2/8gb while q10pro is 2/16gb;
q10pro has a compartment to slot in an internal HDD while q5pro does not.
as far as USB playback with ext HDD is concerned, there should be no diff at all.

if u decide to buy one of these, i suggest to confirm with seller about the latest firmwares.
the current q10pro firmware is 2.0.1 (there is a very new 2.0.3 which i hv not tested yet).
q5pro, i don't know.

From my setup to Onkyo AVR, the volume setting on the Himedia remote will dictate the AVR volume. AVR takes the set volume and then processes it. If the remote set volume is low, then AVR will see a low volume for processing.

Enjoy!

q10pro can send wireless video and audio to another device that has such capability, e.g. q10pro upstairs, play and send wireless to another q10pro-hdmi-tv downstairs.

what u r looking for is to split video hdmi to tv and audio to soundbar wirelessly. i doubt q10pro can split video and audio output like that.

best to keep it simple - either tv arc to soundbar or q10pro optical to soundbar - either way with one cable/wire. the optical toslink cable is a small one.

himedia specific, ask here.

general android box issues, ask in android box thread.

kodi issues, read/ask in kodi thread, answer is there.
https://forum.lowyat.net/topic/3943906/+3340#bottom

read my posts #2561, 2580.

looks like u r very new to this box and not getting help from yr seller.

there are many things already discussed here in this thread, incl input from me.

take time to read at least last 20 pages as people may not respond if it has been repeatedly discussed before.