Is there a strategy in preamp tube placement?

I bought my wide variety of 6SN7s and 12SX7s back in the 80s and 90s. Thankfully, I am not in the market.  I would agree that counterfeit 6SN7s would be easier to detect than counterfeit 9-pin miniature triodes, e.g., Telefunken, but there are many among us who don't know what you are talking about when you use terms like "bottom gettering, a very unique top mica and support structure, including copper posts*".  So, I am just saying know your source.

These days I’d also be leery of counterfeits of tubes that are now 70 and more years old. The best sounding KRs are the black glass variant. You can’t see what you’re buying.

There are many causes of noise from a vacuum tube and microphonics is only one of them. You can test for the other kinds prior to purchase but it is hard to predict whether a tube will be microphonic or not in your home system, because circuitry, cabinet damping and/or direct tube damping, proximity to speakers, typical listening levels in terms of SPLs, socket design, etc, all contribute to the problem or to its prevention.  That said, some tube types are just more prone to the problem than others. In the case of octal base triodes, like the 6SN7, 6SL7, etc, those are just more likely to be microphonic.  Some say this is due to the relatively large size of the glass envelope and the fact that the plate structures are more or less prone to vibrate in the large volume environment.

With KenRad, I've had problems with microphonics that were not totally curable, even in my Atma-sphere MP1 where the tubes are entirely enclosed in the chassis and my MP1 is 22 feet away from my speakers with a couch in between.  However, the problem was "tolerable".  Then I switched to RCA VT231 gray glass in the gain stage.  They're not quite as terrific as the KR but less microphonic, at least the pair I've got.  Much better in that regard. In my Atma amplifiers which sit next to the speakers, I use 12SN7s or 12SX7s (6SN7 with 12V filament); for some reason these are not microphonic at all.

The only principle that holds water is to put your best tube in the gain stage. The last tube before the output jacks is almost always a cathode follower. Cathode follower does not add gain and therefore has little effect on SQ. Except the CF by its nature can add a coloration that won’t be entirely overcome with even the best sounding tube.

while I think this talk about tube rolling as if it was a panacea is blather, I too prefer the KenRad VT231 over all other 6SN7s. But they’re microphonic.