minecraft server and minecraft client can have diferent mod or having just on one side, but you need to check on compatibility.
You can find 3 kind of mod type:
- Forge based
- Fabric based
- Vanilla Datapack
Forge and Fabric are incompatible, but you can use Fabric/Forge mod with Vanilla Datapack.
Optifine is a alternative graphic engine for Minecraft that most of the shaders are made for.
Optifine is not compatible with fabric, but can be load in to Vanilla Minecraft or Forge Minecraft.
Cloudron support just Vanilla Datapack, not any other mod loader (forge or fabric) but been Optifine Client-Only it will work.
But if u wont to add mod that you find on Curse/Twitch you need to w8 later September we will release some version of minecraft apps for cloudron that support Forge/Fabric mod.