You are more than welcome to scan through the scenario listings of each title to get a feel as to what is more popular and what is less popular, based on reported games however, keep in mind that a few years ago, we hosted a Gettysburg tournament, (since that is one of the most popular titles) so you will find the Gettysburg title having many more reported games against it, when compared to other titles.
Also, a game like Corinth have been out for many years. Overland on the other hand, was just released a few years ago, so you will see alot more games of Corinth being reported, compared to the current total number of Overland games being reported.
Every ACW title has small, medium, and large sized scenarios.
Some scenarios have the Rebs attacking with the Union on the defensive, some scenarios have the Rebs defending and the Union on the attack, and other scenarios are designed as meeting engagements in which both sides have no predefined lines and the battle can take place almost anywhere the two opposing armies happen to "meet".
I know you stated previously that you already own a Gettysburg title from another game series however, the HPS/JTS Gettysburg has a free add-on in which they advertise as being an extra 20,000 scenarios.
This add-on can be found here:
https://www.theblitz.club/message_boards...?tid=61609
It is normal for us to always suggest to people who are brand new to the series to purchase a title that they enjoy as it will make the learning curve more enjoyable and not get hung up in "which title is everyone playing the most".
You shouldn't have any problem finding an opponent, no matter which title you choose.