perf Documentation: Add some more hints to tips.txt

Add some (hopefully useful) hints to tips.txt
Also some minor corrections.

Would probably good to make it a reviewer rule that if generally useful
options are added the patch must add an example to tips.txt

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240131021352.151440-1-ak@linux.intel.com