It should work fine. Many users use Mutagen on multi-GB codebases. If we're talking something larger (say 10s of GBs or TB-sized monorepos), then there are some tweaks you can do to make life with Mutagen a little easier. Feel free to reach out to jacob[-at-]mutagen.io if you have a specific use case, or pop over to the Mutagen Community Slack Workspace[0] to chat.
[0]: https://mutagen.io/slack