you can also use $NVIM_APPNAME if you want a more "full" switch between configurations. especially helpful for trying/switching between distributions (i use it for switching between my own config and lazyvim). basically, it modifies the paths where neovim looks for config and data files on startup:

config path: $XDG_CONFIG_HOME/nvim/ -> $XDG_CONFIG_HOME/$NVIM_APPNAME/

data path on Windows: $LOCALAPPDATA/nvim-data/ -> $LOCALAPPDATA/{$NVIM_APPNAME}-data/

https://neovim.io/doc/user/starting.html#%24NVIM_APPNAME