What happens with arousal is called tenting and ballooning, the vaginal canal extends as the cervix contract. The vagina is a muscle that hold it together, so with arousal it get relaxed and with arousal more fluids is produced to lubricate. It is correct that the clitoris get erect and that the clitoris is an organ that is mostly internal, and parts of it surrounds the vaginal opening, but I think the muscles most be included when describing the process. I could speculate that because vulvas look different and that clitoris can be located further or closer to the vaginal opening, perhaps this effect would be more pronounced on some people?

Penetrating sex when the vagina isn’t aroused, could be experienced as tighter, this isn’t really something to strive for as it could be painful and not enjoyable. Just as all muscles in the body using them make the person stronger, so it is more logical a person who had lots of sex have stronger muscles.