SP41 has a silicone grease inside so you have to be careful if you use additional lube in case it gums up.
As for inners….
I have the black PTFE shimano XTR ones on one bike, I bought them as a full kit (£20) as separately they are bloomin expensive now. On another bike I have shimano stainless only inners and I also have some Clarks black PTFE ones.
I do think that the shimano cables are smoother as I think they draw them through a die. The Clarks ones seem to have a coarser surface.
I use the XTR rubber dirt shields on the exit up to the derailleurs and on interupted outer bikes I use the £3 Transfil sealing kit in the outer breaks.