From Inverness, I'd cut across to Kylescu and then come down the coast through Lochinver to Ullapool, taking in the Coigach peninsular on your way.
Something like this
https://www.google.com/maps/dir/57.5076577,-4.2605047/57.2399732,-5.8438777/@57.7500677,-5.2696971,9z/data=!4m29!4m28!1m25!3m4!1m2!1d-4.8953909!2d58.3020532!3s0x489029f30e887e27:0x550280c9395f4c5b!3m4!1m2!1d-5.3042386!2d58.2256917!3s0x488e27d09123fdbd:0x9ef25a6d8efcc096!3m4!1m2!1d-5.2630568!2d58.1277939!3s0x488e25823d110de5:0x8502b5f4e627bec6!3m4!1m2!1d-5.3514094!2d58.0381936!3s0x488e3b7b4631b58f:0x2648cf354fe520d1!3m4!1m2!1d-5.5816799!2d57.7836905!3s0x488e6eafb7858d53:0x58c6b49d10827f4d!1m0!3e0