I'm trying to "upgrade" from valgrind and understand the more advanced tools available but I'm having trouble understanding how perf relates to eBPF.

I can't quite makes sense of your description "BPF makes perf tracing programmatic, and takes perf from being a counting & sampling-with-post-processing tracer, to a fully in-kernel programmable tracer"

Are you saying eBPF can make your programs trigger perf tracing on-demand?