Does stretch and fold give you crisp baguettes and ciabattas ?
A crispy thin crust comes from a few key factors: (1) gluten development, (2) shaping and scoring, (3) steam and venting, and (4) baking temperature. Without strong gluten structure, oven spring will be limited as the dough won’t have the extensibility and strength to expand and hold its shape. Shaping and scoring matter too—they control the direction of expansion in the oven. But for oven spring to happen at all, you also need enough steam and a high baking temperature.
As for gluten development, stretch and folds are more than effective. I only use slap and folds when working with very high hydration doughs—typically 78% or higher.
Slap and fold is performed for about 6 - 8 minutes after autolyse and before bulk fermentation. It’s a lot of work and you need to be comfortable handling very sticky dough with no bench flour.
Stretch and fold is performed after autolyse and during the beginning of bulk fermentation. For my everyday sourdough, I autolysec one hour; bulk 4 - 5 hours, with 4 sets of stretch and folds in the first two hours. The last two sets are coil folds as they are the most gentle so to not de-gas the dough.
If you are working with 75% and lower hydration, there really is no need to use slap and fold.