Hi @Srt93 - FFwd doesn’t merge all increments into a Full. How FFwd works is, at the end of however many Restore Points you have configured, Veeam creates an Incremental. Then, Veeam will merge the initial Full with the earliest Incremental and moves the backup chain forward by 1 to be compliant with the Restore Point setting.
Now, I’ve not used Rotated Drives in my environment personally, but as Cary shared from the link he provided, when you swap out a drive, a new Full is created and then subsequent Incrementals after it, until you swap your drive again. And, it repeats itself. That’s hard for me to picture how those drives work with Retention settings to be honest. What I recommend doing is just test it out with test data and notice the behavior to see if it’s what you want. At the very least, you can ping Veeam Support for clarification on how retention works in your job settings with Rotated Drives.