I went drilled and grooved on mine when I last changed them as I thought it might help with brake dust etc, and they seem to work fine. I think they were also part of a deal with the pads, from memory - however next time they are due I'll go with whatever looks up to the job.
I know you can get OEM solid discs, and to be fair anything which isn't in a blue box will do the job, it's just a big hunk of metal after all.
Pads.... I've heard good reviews about the EDC greenstuff, but don't personally think they are worth the extra money. I put EDC ultimax pads on mine and won't use them again. The rears took forever to stop squealing, even with copper grease and a shim in there. They still do it to this day when in reverse, and it still pisses me off. Next time I'll go for big standard pads as a brake place I went to when I'd first had the issue said the pads were pretty hard compound.
I'm guessing because the rear brakes on a P38 do very little of the stopping, they never get worn in properly, whereas a slightly softer pad would.
If you don't want "uprated" discs and pads, then I'd personally stick with either Lockheed/TRW or Delphi. Mintex pads are also supposed to be good (think that's what I took off mine before).
'06 4.2 Supercharged Black/Cream "Jess" -- Bought April 2021 (NZ)
'01 4.6 Vogue Black/Lightstone "Snog" -- Bought Jan 2012
'99 4.6 HSE Cobar Blue/Lightstone -- Sold March 2009
'95 4.6 HSE Epsom Green/Tan -- Traded June 2008