Pre-cooking your chicken won't "make it stringy" unless you overcook it, in which case it doesn't matter how you pre-cooked it. I prefer to pre-cook the birds if I'm doing spatchcock chicken as the pieces cook at different temperatures, so I consider the braai to be the final grill for flavour.
I usually cook them in a marinade on medium strength in a microwave. Continue to check on the doneness. Just before the chicken is cooked, I remove it and let the residual heat cook it through.
Remember that cooking liquid will never prevent a bird from drying out - the moisture will be pushed out of the bird regardless of whether it is submerged in liquid or not - just don't overcook it...
I usually cook them in a marinade on medium strength in a microwave. Continue to check on the doneness. Just before the chicken is cooked, I remove it and let the residual heat cook it through.
Remember that cooking liquid will never prevent a bird from drying out - the moisture will be pushed out of the bird regardless of whether it is submerged in liquid or not - just don't overcook it...