From my observation, using the default DNS provided by the domestic operations services is the best option for resolving domestic domain names, even in cases where there may be some issues. Having a SmartDNS is unnecessary, as the default DNS is sufficient for most users. For resolving international domain names, if you are not using a proxy, the default DNS is generally ineffective, and it is better to use the DNS provided by the domestic operations services. If you are using a proxy, the proxy will hijack your international domain name and send it directly to the foreign DNS for resolution, making protocols such as Google's 8.8.8.8 and Cloudflare's 1.1.1.1 the most suitable for foreign hosts. Based on my analysis, SmartDNS does not have too much significance.