Do high risks such as hpv 16 or 18 cause warts in the mouth? or wouldn't it be warts like on the genital?

Not exactly: HPV type 16 & 18 are high risk types responsible for cervical cell abnormalities that are precancerous and for anogenital cancers. Type 16 is also the cause of HPV-related oropharyngeal (throat) cancer. Types 6 & 11 are associated with genital warts known as condyloma.

16=yes: HPV type 16 is known to cause oral papillomas as well as oral-pharyngeal cancer. These would differ in appearance from anal/genital warts and arise from several separate tissues within the oral cavity. See the image attached.