Default settings provide enabled FSR with ultraperformance preset, all graphics settings are set to low, but fps feels bad. After enabling performance monitoring I've noticed, that GPU frequency permanently lower than 1000 MHz (600-800 MHz avg.). After forcing GPU frequency in steamdeck menu to maximum 1600 MHz (or for example 1300 MHz if you worried about GPU will work on max frequency for a long time) frametime graphic became more stable and fps increased to 40-50 frames per second. With such performance you can choose balanced FSR preset and make upscaling to be more gentle with textures and text