Via Reddit at https://www.reddit.com/r/HarryPotterGame/comments/10zeh67/pc_performance_tips_this_got_rid_of_low_fps_dips/
Editing Engine.ini with the following has helped PC performance across three systems I've tested, which I'll detail out below the edits. Setting an exception for the executable to disable Control Flow Guard also helped and between the two the game is free of unexpected and unexplainable stutters or FPS drops *for me*.
[SystemSettings]
r.bForceCPUAccessToGPUSkinVerts=True
r.GTSyncType=1
r.OneFrameThreadLag=1
r.FinishCurrentFrame=0
r.TextureStreaming=1
r.Streaming.PoolSize=3072
r.Streaming.LimitPoolSizeToVRAM=1
[ConsoleVariables]
AllowAsyncRenderThreadUpdates=1
AllowAsyncRenderThreadUpdatesDuringGamethreadUpdates=1
AllowAsyncRenderThreadUpdatesEditor=1
For r.Streaming.PoolSize, set the value based on the below:
<8GB: 2048
8GB: 3072
10GB: 4096
12GB: 5120
>12GB: 6144
Systems Tested On
System 1:
Ryzen 7 5700 non-X
7900 XTX
32GB DDR4 3600
2TB NVMe Gen 4
System 2:
Ryzen 9 5900HX
RTX 3070 Max-Q
16GB DDR4 3200
1TB NVMe Gen 3
System 3:
Steam Deck