Some say to wait until a full year of age before neutering your cat!
With a female, you can wait until they have their first heat, especially if they don't go outside, or if they go outside supervised. Females in heat are practically dying from horny frustration, so it may be kind to end their misery by spaying them.
Contraceptive pills can be used to postpone the date of the operation, but won't the pills also hinder full development?
Laparoscopic Spay > Ovarioectomy > Ovariohysterectomy:
After spaying a female, she will be in much pain after the sedatives wear off. If you try and pick her up her she may likely attribute you as the cause of the pain. Even if done so gently with support to front and rear feet, she may be feeling fear and struggle, thus hurting herself in the process. It's best to keep her in a kennel, warm inside a blanket, and move the kennel to an area she feels safe and isolated, with a water source and a litterbox. It's a matter of keeping her from hurting herself.
The same applies to males, but they will be more able to control fear and understand the source of the pain.
Antibiotics after surgery is probably not a good idea? https://www.contagionlive.com/view/postoperative-antibiotic-use-provides-no-benefit