Newbie to Roon with Surface Pro + Meridian Prime HA + PSU setup queries and next steps

Hi all, please play nice as I’m still struggling to understand how to optimise my system below despite the great threads on this forum and am running out of time in my trial:

STORAGE: WD Mycloud NAS wirelessly connected to:
CORE+CONTROL+OUTPUT = Surface Pro (2017) i5 8GB connected to Surface Dock then via USB to Meridian Prime PSU > Prime Headphone Amp > Headphones (Fostex TH900mk2)

I also have a Meridian MS600 endpoint in another room.

I know my headphone setup this is against Roon’s advice so am trying to understand whether adding a USBridge would make a significant improvement. As I understand it, the Meridian prime PSU that I have ordered will filter the USB input before sending a clean and quiet supply to the Prime Headphone amp. So does this negate much of the benefit of the USBridge? Also, would it make any difference anyway as my core would still be on my Surface? One thing I would like to retain if possible is wireless access which I believe the USBridge supports with an 11n dongle but I am nervous it will not be as capable as the wireless 11ac card in my surface which has never showed any sign of dropping out.

I’m also really struggling to understand the signal flow and impact of my wireless core. Take my MS600 endpoint for example which is wired to my router which is wired to my NAS. Are my music files being streamed wirelessly from my NAS to my surface through my router and then back from my Surface to my router to eventually end up at my endpoint or is my core simply telling my NAS to deliver the files directly to my endpoint. If the former then presumably the sound quality is taking a hit from going through my surface. I guess my 2 queries are in fact the same - are endpoints hampered by my core or do they do they make my core irrelevant to sound quality?

I should probably add that I am running my setup as bit-perfect with no DSP / volume controls of any kind active in Roon.

Grateful for any advice and guidance to aid my understanding so I can make informed decisions on next steps.

Kind regards,

@Simon_Mirren I have sent you a pm.