The alacritty config have much more possibilities of be configured
Anyway if you want to add more config to this file or to your custom profile.
I recommend you visit the default config file for more information at the Alacritty GitHub repo
https://github.com/alacritty/alacritty/blob/master/alacritty.yml
That file contains all the possible config that can be applied to Alacritty
If you want transparency and your Desktop Environment or Window Manager don't have this option indicate that you haven't a compositor, so you must install one, in my case I use qtile and have installed picom with his respectively configuration
To add the neovim configuration you must to create the nvim directory on ~/.config/ and then add init.vim file to ~/.config/nvim
You can add more configuration to the file searching on the official documentation of neovim