Hi Scott,
- There is no limit on RAM usage for a node (singlestore is run on nodes with a TB of memory). The amount of memory used per node is controlled by the maximum_memory system variable. By default, singlestore will set maximum_memory to 90% of memory on the host (with some other heuristics for hosts with really large or really small amount of memory).
- This depends on your workload. Typically, fewer larger nodes are better then many small nodes. If you just need more memory (and not more compute), I would scale up your hosts if you can.
-Adam