Im using continuity-3.0.0-beta.4+1.20.1 and indium-1.0.30+mc1.20.4.
I have a huge dome of glass blocks, whenever Im near it cost me 40 fps (of the 60 I have normally) leaving me with a mere 17 to 21 fps.
I've used optifine before and that didn't happen.
Thanks for your work

Which resource packs are you using?

ModernArch, which I used with optifine also.
I've tried BSL shaders (on the lowest setting) that run normally at 60 fps in the 'high' setting
I've also tried seus renewed 1.01 (I think), the one Ive always used with optifine but it has the same problem in combination with continuity.

peace :)

Does that pack even use connected textures? If not, you do not need Continuity. Regardless, try running without Continuity anyway and see if performance is degraded in the same way.

I have a Ryzen 7 7800 X3D and an RTX 4070 ti ... when running the Patrix Resourcepack with the 256px resolution i have 170 FPS+ (Vsynced to my monitor) on max renderdistance (32)
on Renderdistance 10 with the BSL_v7.2 on ultra settings I have around 90 -120 FPS
I have Fabric, Indium, Iris, Nvidium and sodium fabric installed
and as soon as I put in Continuity my framerate drops to 50 WITHOUT shaders and it crashes when I try to use one

When using shaders, having a lot of glass nearby can cause a drop in fps by 15-30. If shaders are not used, the fps drops by around 40-45. And even if you disable all functions of the mod in the settings, it will still decrease.