No, depending on the membership package your organisation has selected, the number of nominated representatives or academics will vary. More information on the packages sizes and prices can be found here.
An institutional/organisational membership is managed by one representative of that institution/organisation and that is the strategic contact, there is a possibility to also have an administrative contact (with the same rights as the strategic contact). Both the strategic and administrative contacts are included in the list of NRs and therefore part of the package you have chosen.
Only the strategic contact and/or the admin contact will be able to nominate representatives for the IWA membership.