Many people, such as porn stars, have been in bisexual encounters, but they just do it for money. The gag reflex varies from one person to another. I know you can change your gag reflex with practice. Deep-throating makes for a good porn movie, but I don't think guys like it all that much. Mostly the pleasure obtained from oral sex will be from stimulation from the head of the penis.
Some men like to be teased up and down the shaft and some like to be devoured.
You will just have to ask your man what he likes. Racial differences in sexuality are probably more due to culture than race. I've never seen any evidence that race affects sexual appetite, endurance, or anything like that. We decided to try and save the marriage, but I am having a lot of problems being sexual with her. Recovering from a sexual betrayal is very difficult and very challenging.