I have this problem only with jewel case, for example others boxes like xbox, N64, Dos boxes runs ok, but PS1, Dreamcast, Neo Geo CD with jewel case runs low then 10 fps. that's why i'm assume the problem is the reflection.
There's a big performance issue if you use 3D jewel case in menu because of the reflection effect is causing enormous lows fps in BigBox mode, even in a RTX 4070 ti pc.
I wish there's a way do deactivate the reflection in jewel cases.
I use in two desktops and the same problem.
i7 13700kf
32g ddr5
RTX 4070 ti Gigabyte
HD 4t WD
AMD Ryzen 7 5700G
16g ddr4
RTX 3050 Palit
HD 4t Toshiba