Custom ROMs typically remove bloatware, which can help speed up the phone, especially during heavy tasks like gaming.
Rooting your device, unlocking the bootloader, and flashing a custom ROM will void your warranty. There is always a risk of "bricking" your device (rendering it unusable). The methods described below are specifically for the SM-J700H . Flashing files meant for the SM-J700F (the international model) or other variants can cause severe damage to your modem and IMEI. Always verify file compatibility before flashing. sm-j700h custom rom