You are correct! The Top Air Flow Sai uses a titanium bucket to heat the concentrate, so the material is never in contact with the heating element. To make this work, the airflow needs to come from the top. It hits like a little "rig".
Hits like a champ, and is easy to maintain. One of the best cannabis related purchases I've ever made.
The Sequoia is a larger version of the Sai. Personally, I don't recommend it unless you're a super heavy user. I just don't like exposed coil wax atomizers anymore. There is a TAF Sequoia, but some people are having issues with it. These buckets are all heated by a donut heater. I wonder if the larger Seq bucket is too big to be efficiently heated by a ceramic donut. I have zero issues with the smaller TAF Sai though. That having been said, there are fans of the TAF Sequoia. If you have your heart set on it, don't let me discourage you. You'll just want a dual battery mod.
To answer your last question, the Sai does come in Ti (though I didn't realize the TAF version did until now!)
I have the original stainless steel version. The Ti will just be significantly lighter. If I was buying my TAF Sai today, I'd go with the Ti for sure.
Thanks for the heads up about the 420 sale! Did they list a coupon code, or are just some items marked down?
Edit: I saw you listed "420sale" as the coupon code. Thanks!