Hi
esxtop (press, u,f and add VAAI stats "o") is able to show you some VAAI stats. I'm not 100% sure but CLONE_RD (Reads) and CLONE_WR (Writes) should be able to show you if VAAI is being utilized.
If you storage array allows to monitor IOPS/MBs granular on disks, target ports, etc. you should be able to observe a minor load on the target ports and a higher load on your disks/pool.
Regards
Patrick