VTZF ii 4u would be fine, but I do find that NR900 3u is a bit faster than VTZF2. I have the NR900 and have tried my buddy's VTZF2 (both 3u & 4u), and I prefer my NR900 as the swing speed is a slight faster. Hope this helps.
I will pick BS12. However if you insist on Top top end, and voltric series, then I suggest Voltric Gland 4U. It's definitely more forgiving than zf2 with a bigger sweet spot and still almost as fast as zf2. Sent from my EVA-L09 using Tapatalk