@Paulie1001 

I Personally would guage this on your internet connection currently, and what it is likely to be in 3-5 years time.     

If you have for example 1gbps at present WAN speed, then its likely to fill the connection port on the switch and doesnt give you much wiggle room for expandability.  If budget stretches, multigig 2.5 switches are the answer that way your interlinks are not flooded by WAN traffic, still plenty of capacity.   In this setup you could chain the switches without any hassle and its not uncommon to do this, generally its good practice to have a little (really just one) connection to the router as it introduces latency, going switch to switch traffic should be direct not via the router (ideally).

If you have 1gb ports and 1gb WAN.. heavy WAN traffic will flood whatever port is in use and that can stop any LAN traffic you have to your SAN / NAS etc..

If however your WAN speed is 300/500 and expect that to be the case for a few years..  then 1gb switches are a LOT cheaper and will more than suffice you for the next 2-3 years at which time you can then consider upgrade to 2.5 for a lot less!     You still have plenty of backbone capacity for LAN traffic so its a good option.  

Personally.. connect 1 switch to the Router.. then drop the rest off it via the last 2-3 ports as needed.. thats how most setups tend to be.    Routers introduce latency and should really only be routing traffic between VLANs or to the internet.  Trunk ports on your switch are the answer for this, should be fine then

WiFi wise..  Go WiFi6 unless your budget really stretches to 6E..  again however if only running 300/500mbps WAN then 6E isnt worth the sell for you and stick to 6

  @Philbert 

Thank you for your reply. I am quite novice, so very greatful for any advice. Please correct me if i´m totally confused

As of today the speed from ISP is at 500/500. 

I think 1gb ports is good for the next few years, the SG2218P should be ok, and has enough ports including PoE. 

Have been using Wifi 5 til now, so Wifi 6 should be sufficient. Going for AX3000 (3x EAP653 ceiling APs -one for each floor in main house, and for the garage/movie-room a EAP655 -which also has 3x ETH Gb-ports.

The ISP fiber is a trunk consisting of 3 VLANs tagged "100" (admin) "101" (IPTV) and "102" (internet). This fiber-trunk connects to ISPs own modem/router ZyXEL FMG3542. 

I would prefer to replace the Zyxel with TP-Links ER7206. Any thoughts on this? Or is it even better to use switch between ISP and ER7206? or better to keep the Zyxel but configure to be in bridged mode?

i think the topography should be:  

internet -> ER7206 -> SG2218P -> OC200 + the rest of the house on remaining ports on switch (RaspberrytPi + camerasurvailence-recorder + IP-phone + TV decoders etc)

will this work? i suppose i have to direct the VLAN tagged "101" (IPTV) directly to the port where TV-decoder connects.

I´m also curios if there will be any problem creating my own 3 VLANs for IoT, Private, and Kids/guest, since the internet is already on a specifict VLAN tagged "102". 

  @Paulie1001 

We dont follow that same setup of multiple vlans for traffic from the ISP here in ireland, so personally not experienced it.. hopefully someone else would be able to answer that for you!

However in terms of the creating your own VLANs, yeah no hassle as long as the VLAN tags are different..   for example set your IOT as   120, the Guest as 130, etc etc..  

  @Philbert 

Well, i think i have found a solution.. 

The problem people often have when switching out the ISPs modem-rpouter with own private, is that they have problems recieving live televison.

the ISP delivers fiber trunked with VLAN 100-101-102.    100 =admin, 101 =  television, 102 = internet. 

I plan to use the ER7206 to completely replace the ISP modem-router. I willl put the fiber directly in the 7206, then creat VLAN 101 -tagged on a designated port, and have the vlan 102 untagged on another designated port. 

TV-decoder will connect directly on the port tagged "101" on ER7206, and the IP telephone on port tagged "100". The switch SG2218P will connect directly on an untagged port since internet usually is not tagged.

I will also clone/copy the ISP modem MAC address til the ER7206.

On switch i will create my own VLANs for Guest, IoT, Home.  

I hope this will work!!!