Hi Lee,
hardwood pellets are ideal if you can source them, but we’ve found them difficult to get hold of in the UK, and have had good results just using softwood pellets. Their main function is creating a more open structure in the coffee mix, but we’ve also grown Oysters in bags of 100% softwood pellets as well.
It’s possible that some of the resin content is reduced in the pellet production process under high heat/pressure, and also Oysters are just really versatile and will grow on lots of materials that other mushrooms won’t, so you should be fine with softwood pellets.
best wishes, Adam