Hi, Travis,
Glad to hear that you have good experience using Couchbase. We have seen customers using large documents than 2M.
From performance perspective, yes, you will need to adjust RAM and Disk settings to suit your needs. The bottleneck may come from many place, RAM, Disk I/O or Disk. Please refer to this blog about sizing: http://blog.couchbase.com/how-many-nodes-part-1-introduction-sizing-couchbase-server-20-cluster
Thanks,
Qi