I have to disagree VERY strongly with you regarding titanium. This is urban legend. Ti is one of the most inert materials there is unless you handle it in very particular ways and the nanoparticle argument is complete BS. At very high temperatures, far beyond vaping, I worry about high chromium stainless like 316, so if a person were blowing builds often, I would tell them to avoid using SS. It is physically impossible for Ti to emit anything that will harm you that wasn’t put there during manufacture.
You can take or leave that information as you see fit, I have a PhD and aside from having made and handled Ti nanoparticles amongst many other nano-oxides, I make my living primarily as a materials scientist. I completely agree with you on nickel, but Ti being dangerous, in any way, is urban legend.
One last bit, 316 is passivated and doesn’t oxidize due to chromium. It is not a friendly element, but it is well retained in 316SS. .Ti is self passivating and does not corrode due to an extremely well formed and attached layer of TixOx oxides. These oxides are quite durable, which is why Titanium does not rust, no chromium required…again, take the info as you see fit. I’m not here to argue, but I do debunk the bad info I see RE titanium.