Garbage collected languages like Go will always have worse performance than lower level languages like C (frr and bird are implemented in C).

Gobgp is great if you want to embed it directly into a Go app though. Talos Linux has done that recently.

Nope, it is a matter of skill as well.

https://github.com/ixy-languages/ixy-languages

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.