Will an Ethernet Switch introduce any risks to SOHO security?

Hi, I wish to keep all my internet connections using the 4 hardware ports (3 VLAN).

If I use a cheap ethernet switch with 4 ports on it, can I use that to access one VLAN but everything connected via the switch will be able to see each other?

Also, has the ability to choose one port for Admin access gone in Firmware 7.1.1? I just can’t see it.