- Originative is a hobbyist resale company. It distributes, it doesn't manufacture. GMK is a Germany company that made old Cherry doubleshot keycaps, and they continue to make them to this day. Originative carries GMK-made products, among many other things.
- Originative has sold 2 classic beige sets. One was GMK, double shot ABS, and is now out of stock. It works with standard boards like the Poker 2. However, they also have a full PBT version of classic beige made by BSP. That set is only for winkeyless keyboards, and yes, a lot of mods and caps lock won't work with a Poker 2.
- Imsto's set is made by the same company as the Originative PBT classic beige set (BSP), except it has cyrillic legends. If you buy an RGBY set that has at least 7 1.25x mods and you get a 6.25 space bar and a non-stepped caps lock, you will have everything you need. It won't work out of the box.
The original classic beige set was a full-pbt keyset (not sure who made them). The BSP PBT sets are exact replicas of it. (maybe they said "similar" since the spacebar is missing and it has cyrillic) The doubleshot GMK version is a close copy, but doubleshot ABS instead of PBT, and has the right size modifiers for modern keyboards.
Hope that was all clear.