Best practice is to have at least 3 lead hosts in a small and 5-7 in large cluster. Sync jobs between each lead host will exponentially increase without further improving clusters security. I verified this by asking Microsoft Partner Support.
For small hosting scenarios e.g. with less than 3 cache nodes and where you need an SQL database anywhere it might be an alternative to put Cache Configuration and Cluster Management Role on the SQL Server, using AlwaysOn Availability Groups Feature to ensure High Availability.