Well, after almost half a year of using 50g and 55g gold plated springs I can share some feedback.
First the plating, it looks good but that is less important, the gold plating makes the surface smooth. Compared to non plated springs there is no squeaking or scratchy sound when you press the switch and this is whithout lube. I have compared SPRiT springs with springs from GON (55g) and Originative (50g) and the gold plated feel much smoother.
Also there is a difference in the compression curve, I use only linear switches, in particular MX Black Old or Vintage, the springs from Originative and from GON feel linear, SPRiT springs feel more like topre there is a small resistance at the beginning inthe middle the travel is linear and in the end you feel some resistance making the landing soft. This feel is more accentuated with the 55g springs. As a HHKB user I could say that 55g feel almost as 45g Topre.
All of this is based on my daily usage I don't have any tools to measure this, only my fingers.
For me 55g springs make MX Black feel exactly how MX Red should feel.
50g are bit too light, but I think if your are a floating typing or whatever it is called and don't bottom out these are perfect.
Because I like only light and linear switches I can't provide info on other weights except 68g on the spacebar which is great.
SPRiT has done a great job with the design of these springs
As a side note, forget the graphs for spring weights published in the past, these don't apply to SPRiT springs at least from what I could notice.