I see a plugin available for TFS but not for VSTS
As far as SCM providers go that are relevant to VSTS, Git is supported out of the box for SonarQube and SonarCloud, while a community supported (but currently without a maintainer or support for SonarQube 7.3+) TFVC Plugin also exists, which I’m guessing is what you’re referring to when you say “seeing a plugin available for TFS”.
Both TFS and VSTS support Git and TFVC as source control providers, and I personally encourage the use of Git in part because of the support you get from modern ALM tools (like SonarQube!). Using Git with TFS/VSTS is a truly satisfying experience.
You might also be interested in documentation for Analyzing with SonarQube Extension for VSTS/TFS
And beyond being a good recommendation from @ColinHMueller , this is actually the top recommendation from Microsoft itself ! Article Choosing the right version control for your project :
Git is the default version control provider for new projects. You should use Git for version control in your projects unless you have a specific need for centralized version control features in TFVC.