For Kyphosis we recommend going with any of the following linked products. All braces are adjustable and will help pull your shoulders back/keep your back straighter.
Comfort Posture Corrector:
https://thenaturalposture.com/collections/back-brace/products/wide-strap-posture-corrector
Complete Back Care Brace:
https://thenaturalposture.com/collections/back-brace/products/magnetic-corset-back-posture-corrector-for-men-and-women
If you want to wear something during the day and under your shirt you have to sacrifice effectiveness/comfortability. If you are wearing a button down shirt it is easier to hide either of these:
Upper Back Posture Corrector:
https://thenaturalposture.com/collections/back-brace/products/posture-corrector-back-and-clavicle-support
Adjustable Magnetic Posture Corrector:
https://thenaturalposture.com/collections/back-brace/products/adjustable-magnet-posture-corrector
For forward head posture we recommend doing our neck exercises and stretches since forcing your head back with a brace would require a head apparatus. We email our posture improvement guide after you order which includes step by step instructions(with photos) on how to fix forward head posture and Kyphosis.