DriveHQ FileManager usually uses very little memory. Unless you are working on some very large folders with a huge number of files, it will not use too much memory.
Please note if you are synchronizing a folder, FileManager could use a lot of network bandwidth, making your other network applications slower. Since FileManager always uses incremental upload / download, the synchronization usually only takes a short time, except the first time, which could be much longer dependent on the amount of data and the speed of your network connection.