How can i get more info about a brew formula before installing?

Nope. Homebrew intentionally lets the web sites serve as documentation of the packages, instead of maintaining a separate copy of it.

You can do a brew home <formula> to fire up a browser from the command line, or brew edit <formula> to examine the formula's installation instructions themselves in an editor.

You can get a one-line textual description of a package with:

brew desc FORMULA-NAME

For example, "brew desc terminator" returns:

terminator: Multiple terminals in one window

I use brew [cask] cat [...] to see the exact formula (without necessarily editing it as other answers here suggest). It shows what gets downloaded, from where, with what checksum, what other formuli/casks it depends on, etc. Here's an example:

$ brew cask cat java
cask 'java' do
  version '12.0.2,10:e482c34c86bd4bf8b56c0b35558996b9'
  sha256 '675a739ab89b28a8db89510f87cb2ec3206ec6662fb4b4996264c16c72cdd2a1'

  url "https://download.java.net/java/GA/jdk#{version.before_comma}/#{version.after_colon}/#{version.after_comma.before_colon}/GPL/openjdk-#{version.before_comma}_osx-x64_bin.tar.gz"
  name 'OpenJDK Java Development Kit'
  homepage 'https://openjdk.java.net/'

  artifact "jdk-#{version.before_comma}.jdk", target: "/Library/Java/JavaVirtualMachines/openjdk-#{version.before_comma}.jdk"

  uninstall rmdir: '/Library/Java/JavaVirtualMachines'
end

try this:

brew cask info [package]