How much of the potential benefits were discussed during the Brexit campaign? I thought the campaign mainly focused on the (perceived) negatives of the current arrangement?

All the potential benefits are blatant lies.

Brexit doesn't give £350m to the NHS. Brexit doesn't get us out of ECHR (and that wouldn't be a benefit anyway, since ECHR agrees with UK on over 99% of cases). Brexit doesn't give us control over our spending. Brexit doesn't give us control over immigration.