All warlock or multiclass sorcerer?

[rbstr]

It's pretty important if you intend to primarily attack people in melee.
Do you want to be a sword-swinger or a spell-slinger?

Warlock 5 Sorc 10 is maybe a decent eldritch-smite build. edit: nevermind forgot the warlock slot restriction do not do this to smite. But you're giving up several melee-centric abilities and a hit to your HP.

Quickened True-strike is still junk, it works on one attack on your next turn. Better off with a quickened booming or green-flame blade even with GWM. Two chances to do damage is better than one advantaged chance typically.
Darkness/Devil's Sight or Shadow of Moil are way better ways to generate advantage.