RetroNX (a group of @m4xw, @natinusala and @p-sam) has just released a public beta version for its overclocking and underclocking system module called sys-clk.
You may have heard of another tool called Freebird that has a similar utility, but unlike this one, sys-clk adapts to different games, which means you can have different performance profiles for your games. In addition, these different profiles are automatically loaded as soon as you run them.
These profiles can also be edited on the fly and the changes will take effect immediately.
Finally, sys-clk supports separate configurations for dock and portable modes!
You need a Nintendo Switch under Atmosphere updated with at least the latest stable version.
Copy the config and atmosphere folder to the root of your sdcard, overwriting the files if you are invited.