As per the document It is not recommended to add a large number of worker nodes to a single-node cluster. But we would like to know the recommended number of worker nodes can be added with SNO and the risk associated if we increase the worker count. 

Document: https://docs.openshift.com/container-platform/4.14/nodes/nodes/nodes-sno-worker-nodes.html#sno-adding-worker-nodes-to-single-node-clusters-manually_add-workers:~:text=It%20is%20not%20recommended%20to%20add%20a%20large%20number%20of%20worker%20nodes%20to%20a%20single%2Dnode%20cluster.