CAT6 Audio Streaming, TouchScreen Terminals, Surveillance S

Hello, thank you for reading this post!

I am an IT enthusiast, new to Pi and Linux; my knowledge is limited but I am willing to LEARN.

I am in the process of renovating a house and I’ve had a cabling team pulling 2 to 4 CAT6 cables to several rooms of the house, depending on the room. A total of about 40 CAT6 cables.

My main goal is to Stream Online Music using wired speakers and hook up my HikVision NVR surveillance system.
I would have touchscreen display terminals, TV’s and PC’s in key areas for the following controls:

Speaker routing controls (turning on and off speakers depending on the room, dedicated source; controlling what room plays what)
Online audio streaming (ex.:
Internet Browsing
Kodi media center access
NVR access

I have a few questions since I haven’t bought all the hardware needed I want to figure out what I need to buy ON A BUDGET.

What kind of POE Switch would you recommend (40 Cat6 Cables)?

[b]Can HMDI through Cat (video) and USB through Cat (mouse and keyboard or touchscreen) be easily routed with a SWITCH setup or I need additional hardware (my knowledge is limited, can this be routed with a switch using VLAN or else)?

How many Pis are needed for this setup?

What budget speaker would you recommend? Audio quality is not a priority at this stage but if I need an audio extension device I will buy it.

Is it possible to find budget speakers that will be POE with just one cable somehow using an Arduino setup on the receiving end?

Some speakers would be nearby a CAT socket but others would require a wireless (or bluetooth, whichever is easiest) signal from a nearby CAT socket Access Point. What would be the easiest way to achieve this?

Can all the services (see previous list) be accessible through all display terminal anywhere in the house, including NVR Access?

What budget touchscreen wall mounted display terminal would you recommend for this project?[/b]

Thank you for your help and patience,
Best Regards.