minecraft-optimization VS Tuinity

I'd recommend dropping the simulation distance and render distance and read up on this. Chunk loading is one of the most resource-intensive parts for the server - perhaps even the most.

You have troubles' guide

Follow this guide (read all carefully)

I have since found https://github.com/YouHaveTrouble/minecraft-optimization so I will be reading up on that too!

According to the GitHub Repository, it hasn't been updated since Aug 27, 2021 (currently 15 months ago) and the Repository is Archived, which pretty much means you won't get any support there.

For the server version, there are tons. You've got PaperMC, Tuinity (will be upstreamed to paper soon), Purpur and a lot more forks of a fork of a fork. I personally use Purpur because they're better optimized and faster than Paper. You can read more about them on their respective links.

Actually try Paper instead of spigot. Paper is a fork of Spigot which focuses on high performance and bug fixes. And usually runs faster than Spigot. If you rlly need something to run faster than Paper, Tuinity or Airplane will work

Running vanilla with a lot of players is going to start creating a lot of tps lag. I would recommend running Paper or even Tuinity if you are having higher player counts. Depending on the player count and other factors like plugins, etc, you would want to go for 4-8GB of ram + a higher end CPU.

It's completely free. The server software like Paper, Tuinity, Airplane, and Purpur are completely free and open source. There are tons of them out there, and most remain as open source projects. Excluding the hardware and electricity required to run it, the servers are completely free to host.

With 16 players online at once, it's going to put a lot of stress on the server. So run Tuinity or Airplane (airplane currently supports 1.17), 8-16GB of ram, and a good amount of storage

Always go with a server. The vanilla server software can't handle that much at this point. On realms, there's not much u can do in order to have it run smoothly. But with servers, u can swap the vanilla jar out with Paper or Tuinity, which allows for less lag

Tuinity: https://github.com/Tuinity/Tuinity

1.17 builds are stable enough now! Repo

I would always say that if you want to stick to plugins, always go for Paper. It's much faster than spigot (and here's the reason why), open source, and fixes bugs and exploits that spigot or upstream vanilla won't fix. It's a fork of Spigot, so you get all the features of spigot, and the lag reduction is really good on paper. I would recommend using Bungeecord or Waterfall as the proxy (which is a speical server software that allows players to hop between servers without having to join and quit. if you have played on network servers like hypixel, they use proxies, but it's on a more massive and complex scale), and use Paper or Tuinity as the backend servers (the actual servers you'll play on). Have the lobby server set as the default server, and either use 8 different servers or use 2-4 different servers with Multiverse and create 2-4 different worlds on within the servers.