All photos should be optimized for the web before uploading. This helps to reduce network bandwidth usage, improves site performance and is generally a good idea for the environment. Not only does this make the upload process smoother, your images will be displayed crisply too.
You do NOT need to crop your images, however, you just need to make sure they’re optimized correctly. The system will in any case create multiple appropriately sized thumbnails after the image is uploaded, but let’s not waste each others time uploading RAW images in the first place!