Selfhosted

Firstly the best way would normally be to have a separate switch and router.

The router only having 2 ports WAN and LAN. And then get a great MANAGED switch for your lan.

For your router basically any old x86 PC loaded with OPNSense would be great.
The network card you will buy depends of your internet speed.
(And try to find Intel chip network card)

Next for the switch, definitely get a managed switch (you won't regret it).
The number of ports depends on your needs. Basically a 8 ports could be just enough or maybe very too little.
That really depends.
For the switch port speed it again really depends. Do not get 100Mb switches at least. But the sky is the limit.
1G is plenty for a lot of people. But 2.5G could be good too. (In my opinion 10G is overkill for most of the people)
The problem is that switches prices are exponential with the speed. You can get really good 1G for cheap. More difficult with 2.5G and impossible for 10G.
And lastly PoE or not PoE that's the question. I would say a huge NO (except specific use cases). If you got 20 cameras, 38 motion sensors and 76 APs, YES a PoE switch is a good idea.
If you have a small amount of PoE devices, simply buy a cheap unmanaged PoE switch.
If you only have one or two of them, just buy injector.

If you have any questions concerning a brand or anything else feel free to ask

EDIT : formatting