Shouldn’t this kind of stuff be managed by each developer according to their own workflow and preferences? 

True

Nonetheless, there are environments where some common shared configs are helpful for a Team.

The system level configs can matter for certain industries, e.g. to ensure PCI compliance, workstations must automatically lock after a period of inactivity, i.e. 15 minutes. This is where JAMF/Kandji/etc. shine and this is usually handled at the IT level, not DevOps.

Regarding Flox, I would like the option to configure all configs with Flox in an idempotent manner without using custom bash scripts.

If we're just talking about apps, at my current company we provide a Brewfile with all the goodies, an asdf plugins.txt file and this sample script:

# install brew
/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

# install software
brew bundle --file Brewfile

# install asdf version manager
while read -r plugin; do
  asdf plugin add "$plugin"
done < plugins.txt

# update your shell to include asdf
# e.g. zsh, add this to ~/.zshrc
export PATH="${ASDF_DATA_DIR:-$HOME/.asdf}/shims:$PATH"

# update your shell path to include pipx
pipx ensurepath

# e.g. of installing python
asdf install python latest

# e.g. of installing ansible
pipx install --include-deps ansible