I'm currently working on making a modpack for Minecraft to just play myself and maybe with a few friends. I'm making it in version 1.12.2 and have quite a few mods in it. The problem is that it is running with really terrible fps. It has no problem loading up or on the menu screens but once you load into a world and play it for a bit it just is laggy and has terrible fps. I'm wondering if there are any ways that I can speed up the fps and/or increase the performance of the modpack. Also, I have increased the memory of Minecraft to a very healthy amount and it doesn't ever reach it's limit and doesn't even have a very high memory usage anyways while playing.
Question: How can I improve performance and FPS in Minecraft for this Modpack? How can I improve the Modpack? Any insights or comments to provide?