Who is your ISP? What service connection is being provided: coax, DSL, fiber?
What make and model modem, router, or modem/router (if combined)?
If you have admin access to those devices you can learn a great deal about your network. Routers often provide some sort of listing or even a diagram/map of connected devices.
You can run "ipconfig /all" (without quotes) via the Command Prompt to obtain specific configuration information for each connected computer.
You can use "arp -a" as well to learn more about the network devices that each computer may be communicating with.
My recommendation is to start with a simple network diagram showing all known network devices. The diagram does not need to be a work of art or unduly complicated.
I counted 8 devices but you mentioned camera's as well. Any IoT devices that need to be included?
Just show the devices, label them with as much as you know about each device and how the various devices are physically connected or indicate a wireless connection.
Device name, MAC, IP address, etc.. Include patch panels, wall jacks, etc. as may be part of the network. Could be some bad or loose connection somewhere. How far apart are the devices. What is between the network router and the wireless devices? Walls, appliances, different floor levels, etc.?
Go online and look for example "home network diagrams".
Get a sense of the big picture and where problems are occurring. If only your PC is affected then try another known working, at speed, Ethernet cable between pc and router.
Verify that only one network adapter is enabled on your pc - either wired or wireless. Not both adapters at the same time.
Check that speed & duplex are set to Auto.
Try disabling IPv6.
Look for duplicate IP addresses.
Test connectivity and speeds with all other devices offline. If the speeds are as expected then bring other devices online but only one at a time and allowing time between additions.
The devices may take some time to establish handshaking and subsequent network communications there after.
Start with a diagram and go from there. Not as difficult to do as you may think.
And if you wish to do so, feel free to scan in the diagram and post here via imgur (www.imgur.com
May prove very helpful regarding other questions and ideas.