Everything is spot on, exactly what you want
The service, the servers, it's nothing but fantastic. Will help you with whatever it is, even if you're slow like me they help amazingly and keep their cool. Nothing but love for the guy, an amazing soul.
On a Paper or vanilla server, memory mostly goes to the chunks loaded around each player, which is why player count and view distance matter most. A view distance of 12 loads over 40% more world per player than the default 10.
Modpacks are different: every mod is loaded into memory when the server starts, before anyone joins, so a 150-mod Forge pack needs several gigabytes on its own. Plugins on Paper are much lighter.
The calculator adds those up from data we collected on Minecraft servers, then leaves about 15% headroom so the server never runs right at its limit. It's a guide, not a promise, and you can upgrade from the client area at any time.
Quick answers about Minecraft server memory.
2 GB is enough for a small Paper server with a few friends. A community server with plugins wants 4 GB, and most modpacks need 6 to 8 GB.
A light Fabric setup runs in 3 to 4 GB. Large Forge or NeoForge modpacks with 150 mods or more need 6 to 8 GB, sometimes more.
Yes. Each step up in view distance loads a lot more of the world around every player. Lowering it to 8 is the easiest way to save memory.
Paper uses about the same memory to start, but handles busy servers far better and runs plugins, which vanilla cannot.