FastSCP allows you to copy directly between hosts so it can save you a bunch of copying time. I'm not sure what you mean by "manually" copying the files. Do you mean using the vShpere client and downloading the files to some location then uploading them to the new host? Either way will work fine, but FastSCP should save you a step.
If you currently have snapshots, you can consolidate first or leave 'em and just copy them with the rest of the vm. There should be no need to do anything with the snapshots if you are doing an "offline" migration. As long as you grab all the files, the snapshots will show up on the destination host when you register the vm on the host.
I've done "online" migrations of large vms by first taking a snapshot on the source host, copying the base disks to the destination host first while the vm was still running on the source host. When I was ready to migrate CPU processing, I would power off the vm, copy the remaining files (which would include the disk deltas and whatnot) and power up the vm on the destination host (which would only cause a few minutes of downtime). Later, I would consolidate the disks by removing the snapshot over on the destination host. A poor man's way of doing a vm migration across ESXi free edition with little downtime.