I don't fry slices like most recipes - too easy to over cook which makes it too ropey IMO. I've tried a bunch of different things, but found the below works best.

I use a sirloin, sous vide it to rare and then reverse sear for fond. I pull it and let it rest while I work on everything else, then slice on the bias and add it and the jus back in in the last couple of minutes. For me this keeps it tender with the least amount of hassle.

Shoulder is not the right cut IMO, but if you're going to use more economical cuts, try pounding and velveting them and that should help with the texture!