anti-aliasing settings

I use a downsampled rendertexture size of a camera (352x264). To downsample I need antialiasing otherwise I would get very strong spatial aliasing.

I am using the built-in renderpipeline, in the quality settings I setup 8x Multi Sampling Anti Aliasing and I use the postprocessing stack where I apply SMAA.

I see there is improvement by applying these but it just does not seem enough…
I am wondering if I am missing something.

Thak you for your answer.

problem fixed here : Setting anti-aliasing of already created render texture is not supported unity - YouTube