Giant Conduct mechanical/hydraulic disc brakes

I’ve got the Giant conduct mechanical/hydraulic brakes on a TCR 1 2019 and despite what everyone says I think they are very good; probably better than the Shimano 105 lever/Ultegra caliper mix that I have another bike.

I don’t think that this bike requires a brake bleed but the barrel adjustment on the headset (mechanical part) is pretty much wound all the way out on both front and rear.

I feel I could do with more on the rear brake but I cannot get at the grub screw despite the barrel being wound all the way out. The barrel needs to come out a bit more for access but it’s on the limit. HELP?

I understand that’s all I need to do is slacking off the torx 15 screw, pull the cable tight, re torque the screw and then wind the lever back in. Ideally I would get the cable just tight enough so that when I wind it all the way back in I have the maximum amount of future adjustment? Is that what everyone else is a understanding is?