I harp on that particular multiclass a lot because it's less powerful than being a single-classed sorcerer, not because it's outright bad. I'd still rather play a sorcerer/warlock than a few other base classes. If you had to do it, you'd want the warlock levels early, 2-4 ideally, to get the delayed progression pain out of the way. Just remember you're going to be 3 levels behind on spells to get... Cha-based weaponry and cantrip optimization.
If you use standard array with an ideal race, the gap between Cha and Str/Dex won't be significant until you've fully sunk 1 or 2 ASIs into Cha, and you're delaying ASIs. I'm assuming you would not dump Dex even if you went with a Shillelagh build, because why would you dump Dex over Int and Str?
A Scourge Aasimar can get 16 Con and 16 Cha to start off with, leaving a 13, 12, 10, and 8 to distribute. The gap is +2 Cha over Str/Dex at least. Maybe that's worth it. Then again, the advantages of being a Scourge Aasimar don't rely on you using a weapon or casting only cantrips.
A Half-Elf can get 16 Con and 16 Cha to start off with, then boost the 13 to a 14 for Str or Dex. Then the gap is only +1 in favor of Cha. IMO that's not worth delaying ASIs and spell progression.
A variant Human can get 16 Cha, 14 Con, and 14 Str/Dex. That's still a gap of only +1, and they get a feat. There's unfortunately few choices for a +1 Con or +1 Cha feat, though you could start warlock instead and take Resilient: Con, placing the standard array 14 in Con and 15 in Cha to end up with 16/16 after racials. Still, that gap is only +2 and you used a feat that could have been War Caster with innate Con save proficiency.
PB makes the multiclass less desirable because the Scourge Aasimar can PB 15 Con and 14 Cha with a 14 for Str/Dex with points to spare, and the Half-Elf could PB 15 Str/Dex and 15 Con with 14 Cha, erasing the gap until level 7. The variant human can similarly PB 15 for Con and Cha with a 14 for Str/Dex and have something left over.
It's the paradox of the Shillelagh build: It makes the most difference with the accumulation of ASIs that you're delaying by multiclassing for Cha-based Shillelagh. You'll only get a big enough gap between Str/Dex and Cha if you're rolling for ability scores or you pick sub-optimal races.