Choosing a good transformer architecture

Hello guys, I am new here and I have a problem with choosing good transformer model, for my Question and Answer task. I need to provide only question, when validating, as an input (not also context) to my model and I need to get answer. But model needs to be trained on domain data, like documentation. So I am not sure if I could use some sort of generative model, because I needs to have accurete aswer. If somebody could answer I would be grateful. Thank you and Have a Nice day.