There are two ways of using Freetube, either with YouTube’s APi or with Invidious’s APi.

When using YouTube’s APi you won’t get the same ad-blocking and proxying benefits compared to Invidious’s API.

One bonus of using Invidious is that your traffic is combined with everyone else’s who use that same instance, for example if you use inv.nadeko.net your traffic will be masked along side everyone else’s who happens to use that same instance.