Thanks Jay - that has been my(much shorter) experience as well. The LPKF and T&T bits work well so far. I did get bits from a couple more suppliers too. I should put some holes in an aluminum block to build a little plastic locator ring adjuster.
The Harbor Freight Warrior Carbide Rotary Micro Bit Assorted Set(Store SKU 62379, 44924) were uniformly rung differently from LPFK ringing. At full Z depth, they would barely drill the bed. About half had nice ring labels.
I ordered a few different mill and drill kits from AliExpress. These were all labeled "XCAN Qualified 107" through Hangzhou Xuchuan Trading Co Ltd. Unlabeled rings. No three were rung to the same depth.
In other news, I believe I found my 2.95mm x 43mm reference drill bit, and measured it against my LPKF starter pack 2.95mm x 38mm drill bit(apologies for the freehanded couch-drawn diagram).