An experienced bounty manager will not guarantee any profit. It only reduces the risk that a bounty campaign turn in to scam.
The most important thing is the bounty pool and its allocation.
Many bounty pools and allocations cannot be guaranteed by the bounty manager because there is no escrow service. But for the bounty manager, I really trust @julerz12 because the bounty allocation is already stored in the escrow service, so token distribution will be guaranteed to all bounty hunters.