~7.2 GB (Base + Update + 6 DLC packs).

However, for homebrew and emulation purposes, users often turn to specific websites. These sites typically aggregate NSP, XCI, and update files. It's important to be aware that such sites exist, but they operate in a legal grey area and can pose security risks.

Note: It is highly recommended to install Wreckfest on a high-speed microSD card (Class 10 or UHS-1) to ensure the fastest possible track loading times. How Updates Optimize the Switch Experience

includes all the signature modes found on more powerful platforms: Review - Wreckfest (Switch) - WayTooManyGames