VR headsets have a much smaller field of view than viewing content on a browser, and each headset has a different field of view. The software moves the fixed position items towards the center using algorithms based on each headset, but the general rule should be to not put it all the way to the edge if you intend on running it on a headset as well as run in the browser. I generally use “one grid line” from the top/bottom/left/right as a guide when creating content for multi-platform.
Objects appearing larger in VR is also a function of the field of view. Keeping this in mind while designing should allow you to create content that works well on both platforms. Also keep in mind that VR content should be more audio/visual than textual, so you want to try and keep text to a minimum while designing in this new medium.