Does a white coating on the tongue generally mean that one has candida in their gut?

No. Far from it. White coating on tongue does not necessarily indicate anything in the gut.
Candida in gut? Hello~ Depends. If tongue scraped and chked and if def candida, then if severe and prolonged its certainly in esophagus and probably in gut. Chk with stool culture. If present ask why? prolonged or frequent antibiotics, Rx with steroid/inhalers, chronic re-infection (oral sex), generalised debility, HIV infection. Rx difficult and decide if necessary. Severe oral candida gives sore throat.