What is the best way?

[ICR]

Having two folders that may contain folders and files in both. If they only exist in one of the folders what is the best way to merge them? So both folders may contain the same list of folders and files. Also what if the two folders contain the same files, with the same names but different content in each of the files. Is there a way to merge one folder into the second one knowing it may contain the same file but will it add something to the file name. So the second folder would contain everything. Running into because one drive has desktop but it is not syncing because one drive is full. Desktop on the pc I can see is different in some ways but some files and folders exit both places. They may be the same content but at the same time may be different. Same name...

[xCSxXenon]

Doesn't sound like you are using FFS for syncing, rather your goal is to merge two locations. Just use the built-in copy-paste and when it asks what to do with files that have matching names, you can choose to keep both and have it rename one of them to "filename (2)"