I only know one chemical process to produce Amphetamine Sulphate and don't believe that has changed over the years, same precursors same process AFAIK.
What has changed is the habit of moving the stuff whilst it's still soaked in solvent wash, I presume that this has just become 'acceptable' and now no one in the change wants to lose out by drying the stuff. To make matters worse many people cut it and cut it whilst adding more random fluids.
Back in the day the stuff arrived from the lab in a putty form IME, supply was much more reliable, the stuff was so cheap I guess no one though to cut it beyond the normal cur that was carried out on the first pass, prior to everyone and his dog / cat claiming they were selling 'base'.
I always dry the stuff out these days, I'm not keen on industrial solvents

it's hard to be sure of the source and chemical makeup but in recent years the stuff I've had, allegedly from eastern Europe seems more euphoric, dilated pupils etc, the Dutch stuff less so but it does depend on how much you do (obviously and assuming it's not shite) and how long you've be on the go for
I tend to prefer snorting the stuff, eating it never has the same kick although a few gel caps are far more discrete than racking up lines on your mobile phone :D