For optimal performance with just two players, 4GB of RAM is plenty. To keep things running smoothly, consider installing PaperMC, which is a high-performance fork of Spigot and is known for reducing lag. For a mostly vanilla experience, you can also use lightweight plugins like ClearLag to help manage server resources. Fabric is another server mod that supports performance-enhancing mods and datapacks without altering the core game mechanics.