I will travel to the USA in October to attend a friend's wedding. I will also be visiting a lab afterwards on the same trip (I was invited to collaborate without any remuneration). The total duration will be 30 days (2 weeks wedding/vacation, 2 weeks lab visit). I can provide evidence of my invitation to both the wedding and the university.
I am a UK citizen with a valid ESTA. When going through the CBP check what do I say the primary reason for my visit is? Do I apply for the W-T or W-B waiver? Or is it possible to do both?