It depends on what you want. If the surface you are displaying this on is flat, reflection vector will literally just “reflect” or flip the cubemap along that axis. but if the mesh you display it on is round like a sphere, it will actually bend the reflection along the vertex normals resulting in that spherical mirror look you see in the preview above.
using cameravector is basically like you will be looking a screen space projection of the cubemap. it won’t matter what the geometry you put it on looks like or how it is rotated at all. Think back to like 1990’s skyboxes in ue2 where you had a separate environment for skyboxes and marked surfaces as “skybox” and it would just render the second scene without any parallax.
btw when using the 3 basic worldspace vectors that you did (1,0,0 ; 0,1,0 and 0,0,1), you basically return an unchanged vector since reflection vector is already in worldspace… but it should work as those 3 basis vectors change as long as they stay orthogonal (all 90 degrees to eachother).