Scheduling visa appointment with primary eligible for dropbox but dependent not eligible for dropbox

Does anyone have experience where the primary applicant needs to renew the H1visa (visa stamp has expired) and qualifies for dropbox but the dependent H4 is first time and therefore is not eligible for dropbox and needs an in person interview? Is there a way both can still go for an interview together? How do we book the appointments in this case?

Also does this have to be sequential where primary first applies for dropbox; waits for complete process of getting back the passport with the visa stamp and then the H4 dependent books an in person appointment to take the primary person’s passport copy as proof for approved H1 visa? Can this be done paralelly?

I heard that currently the drop box processing is taking very long time (is this true?) and it is much better to go for in person interview for both primary and the dependent