Download either "Upscale" (free tweak, forgot the package) or "LittleBrother" (paid, on Bigboss) and change the resolution to 1242x2208 (or 621x1104 For LittleBrother). It doesn't look that much different, but performance is improved overall.
Be very careful using Upscale, since inputting the wrong values can cause the device to not turn on, forcing either a restore or SSHing into the device. LittleBrother is safer, since it uses substrate and you can always boot into no substrate if you make a mistake.