The general risk of having a potentially insecure device in your network is that it might be used to attack other systems - both inside and outside the network. While you specifically ask for devices from China this risk depends not so much on the origin of the device1 but on the security. And the cheaper a device is, the more likely is that the vendor did not invest much time into properly securing the system. And yes, most cheap devices probably come from Chinese vendors, are produced in China or have at least Chinese hardware and/or firmware inside.
Given that you have your insecure device in the guest network and assuming that the guest network of your router provides proper isolation to the network where you have your other devices, then there is little risk that the insecure device can directly attack your important devices.
And most routers with guest network neither provide access to the router configuration directly from the guest network nor indirectly via internet. But some routers might do or might be configurable to do so. Which means you need to check what your specific router model and firmware version and your specific configuration of the router provides (just saying that the vendor is "Motorola" does not provide enough detail to determine this). If the insecure device can attack the router then this will be trouble for your important devices too, because the router usually provides DNS service for these device and attacks against the router like DNSChanger will therefore harm all devices behind the router.
Apart from that the insecure device might be hacked and misused as part of a botnet - as in case of Mirai. Such a botnet is then used to deliver spam and phishing mails, mount DDoS attacks and infect more systems. While this might not directly impact you, it will impact others. It might also result in your ISP tracking such malicious activity back to your account and limiting your internet access in order to reduce the harm coming from its own network.
In summary: make sure you get your devices (camera, router, ...)
from a vendor with an established good security record and who provides quick and ideally automatic updates in case of security problems for all the years such a device will be used. This kind of requirement usually excludes the cheaper vendors but does not automatically include the more expensive vendors.
1 One might argue about explicit government-mandated backdoors in devices from specific countries. I don't believe that these exist in most devices since too much trust would be lost if they get detected. And they are usually not needed anyway since these devices usually have enough inadvertent bugs inside which can be used for hacking.