The Install Guide recommends installing the software using archives (not Composer) for a shared hosting environment.
However, from Magento documentation:
Everyone who uses the Magento software must install Composer to update components and Magento. If you install Magento using an archive, you don't need Composer to install Magento, but you do need Composer for updates.
And from this article:
Attention: Because Composer relies on third-party code, we do not recommend Composer for use on production sites.
Then what is the "best" way to install Magento 2?