I was watching this video on Youtube by Matt Risinger where he is talking about insulated studs.
They are to replace 2x6 or 2x8 wood studs with what is essentially 3x6 or 3x8 studs. Looking at the web site, it seems like they are primarily targeting the 2x6 market because that is what they are advertising, but the video discusses the 2x8 replacements too.
The 6" thick studs have an R value of R20 and the 8" thick studs have an R value of R30. The video discusses how they are stronger than the 2x6 studs they replace and it's recommended that they are used 24" on-center spacing. The cost is reported to be around the price of LVL wood.
I thought about using SIPs or ICFs for new construction to save cost over a double staggerwall type construction, but if I ever do build a new house, I might consider the R30 insulated studs with cellulose insulation. ..although I really would prefer R40, so I would probably consider furring another 2x4 of normal lumber on the inside for another 3.5" of insulation for the wall cavities to get there. ..because why not superinsulate