How to separate networks completely but still provide internet to both?

So here's a little backstory. We recently got fiber at work. I ran the cat6 installed switches and everything of the sort and I connected 4 stores together. We have roughly 200 devices on the network. Now among those are some IP based cameras that were previously all connected together then plugged into one of the stores so they could view them. After switching over to fiber the cameras were integrated into the whole system and because the 4 stores are connected they seem to be lagging a bit. I want to know how I can separate these cameras from the network and still provide access to them and the internet on 4 computers that need access(via Ethernet cable)

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Setup is like this

Fiber Router > 24 Port switch >cat6 cable to 4 smaller switches for each store > 1 router for each store connected to the smaller switches > Computers connected to routers.

the cameras are connected to one of the smaller switches currently in one store.

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Here's the ideas I have.

Get another switch, plug all cameras into it and then plug the router into the switch to provide internet.
Problem I see occurring: Pretty sure this is just the same network and therefore won't take up any less bandwidth but I could be wrong.

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Solution 2: buy another switch and 4 wireless adapters for the computers, hook up computers and cameras to an intranet with no connection to previous network, wifi connect to fiber for internet.

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Problem: Costs more but pretty sure this works.

Any ideas i'm missing?

TLDR: Cameras are laggy cause there's so many devices on the network, how to separate them from the network but still provide internet to the 4 computers that need them.