For my older son,(who did not showcase - played Legion ball) he got all of his college recruitment from playing for his scout team. They played against other scout teams and Junior Colleges as well. It was a great experience.
In our case the team was run by a professional scout and some of his associates, funded with MLB money that is budgeted to run the team, ie. wood bats, balls, unis, etc.
The line up changed from week to week, pitchers generally got two innings, sometimes more.
The coaches are constantly evaluating you on the field, in the dugout, your interactions with your teamates, you won't know it, but they are watching closely, and making mental notes-those notes later make it into their laptop, or on your prospect card.
If you get invited, you should definately go!