Anything you connect to your network is a potential pathway through vulnerabilities for hackers to gain access to all of your devices. Even smart light bulbs have been found to have certain vulnerabilities to allow hackers to gain access. The latest advice from the security community is to use the three router process where you use each routers NAT capabilities to create two separate isolated networks, one for your IOT devices and one for your PCs and phones.
See https://www.grc.com/sn/sn-545.pdf for a description of the Three Dumb routers configuration.