The Mainstream includes different lottery-offers, e.g. win an iPhone/Samsung/PS or different vouchers, etc.
Sweepstake vertical accepts all traffic types and covers all geos.
Paid actions are different and depends on offer, it could be soi/doi registration or CC submit.
The most suitable traffic for this vertical is common mainstream. As for sources it can be FB target, push notifications and others.

Did this answer your question?