RAM is the setting that most affects a game server. Too little and the world stutters or fails to load; the right amount and it runs smoothly. Here is an honest starting point by game. Mods and bigger player counts push you up a tier.
Minecraft (vanilla or Paper), Valheim for a small group, Terraria, Counter-Strike, Team Fortress 2, Garry's Mod and a Mumble voice server all run comfortably on the 2 GB Starter tier. Heavier Minecraft modpacks (Forge) want about 3 GB.
Rust, ARK, Palworld, V Rising, Satisfactory and DayZ generate large worlds and want at least 4 GB to run reliably, and more as your player count or mod list grows. We provision these at a sensible floor so a fresh world never lands below a runnable size, but matching your plan to the game gives the best result.
Use the starting point above, then add headroom for mods and players.
More concurrent players means more RAM. A busy server wants the next tier up.
You can move up a tier later from your account; your world and settings come with you.
Straight answers.
For the heavier games we provision at a reliability floor so a fresh world still runs, but the best experience comes from matching your plan to the game and player count. You can scale up any time.
It helps, but the game and your settings matter too. As a rule, a busier server wants the next tier up for smooth performance.
Yes. Move up or down a tier from your account at shop.overnight.host; your world and configuration carry over.