Hello Mojang. On MC 1.15.2, My performance is poor in-game and my system's resources are not being used up too much. I first updated 1.15 and I just learn you guys implemented a new rendering engine, which is supposed to be superior to the old one. With the settings I had from 1.14.4 were kept and I saw the game running at 40-30 FPS. I tested this with MC 1.14 and the game ran it a smooth 144FPS. Two days ago, I switched the settings and the game was back up to around 80-120FPS. I don't know why this is happening. Here's my specs. My Nvidia driver is at the latest, and Windows and Java are up-to-date. There's no faults in the PC either. I'm also using the Java version built with the launcher.

Specs:

CPU: AMD Ryzen 2600 @ 3.4GHz
RAM: 8 GB 2400Mhz
OS: Windows 10 1909 64-bit
GPU: ZOTAC GeForce RTX 2060 6GB
SSD: 400 GB (205 GB used)