No they won't. They are generally faster in throughput than any non-gc application that isn't heavily hand optimized. Their problems are higher memory usage and unpredictable latency, not speed.
Just look at the code. Anywhere you like. There's nothing I can say that will be a substitute for seeing it yourself.
I've had to use it as a library sometimes, and it's also really poorly designed as a library. There's no consistent principle for what is exported and what remains internal, so almost anything non-trivial you do may require you to copy-paste parts of the library code because something happened to not be exported. So you must think, okay sure, but in return for that you get a minimal and stable API. Nope! It also has some of the most API churn of any Go module, already up to /v4 and that's only counting the semver-major breakage they bothered to acknowledge, not the many semver papercuts along the way.
(I have only a rather basic familiarity with go, but was considering gobgp for an infra project...)