Question Updated my Unity install, particles look different and performance is terrible. How do I track down?

I updated my project from a mid-2020 version of Unity to 2021.2.6f1 and my particles changed drastically in appearance. Much blurrier, the Color by Speed acts differently, the particle trail is supposed to be red fast and white slow, but I'll see a chunk of red particles in the middle of a string of white, and I don't know how to interpret that. The game performance will also occasionally hiccup and lag terribly for a second; this may or may not be linked to the particle trail color bug. I did not change any project or component settings to precipitate these changes, they showed up as a result of the update, so I'm hoping someone can tell me some Unity settings I can check that might have been changed in an update over the past ~year. The shader pipeline changed from LWRP to URP which may be related? I've tried switching around the shaders, materials, and settings for both, and a bunch particle settings with no success. I've tried using the profiler but could not find a reason for the performance hiccups. What else can I check to hunt down the issue? Thanks.