Disabling the "DNS client" in Windows will not stop you receiving web pages. Generally you receive dns records from your service provider. "DNS client" service simply acts a cache.
However it will slow network searches down or browsing for other computers on your network, because it will have to build the list every-time. So if you have only one computer on your network, no biggie.
If you have host files, then disabling "DNS Client" service is not any issue, nor is it a real issue in the first place.
No turning off your DNS client does not clear your cache. Benefit none really except a little speed increase. People get this idea that it will stop pop-ups and block ads, but most browsers will do this for you.