All guests must be invited to and will be asked to RSVP to the primary event. It's not possible to invite only a select number of guests to the primary event.
However, if (for example) you have a wedding weekend weekend consisting of multiple events -- and not all guests are invited to any single event -- you could make your primary event something to the effect of 'Jules & Chip's Wedding Weekend.'
This way, you will ask guests if they are able to attend your wedding weekend as a whole -- and can then use RSVPify's Secondary Events feature to invite select guests to each of your various sub-events.
Tags: main event, not invite, only invite some, not all guests