SQL Server seperate data files
NDF are not file groups. NDF files are additional data files. You may achieve better performance by adding additional files or you may not, it depends.

Read Benchmarking: do multiple data files make a difference? by Paul Randal.

What I think you had in mind are additional file groups, whereby you create an object in a new file group and put that group into separate file (NDF). To ease I/O, large, frequently accessed tables will achieve better performance in separate file groups, providing those file groups sit in separate files and those files are on different LUNs, and LUNs are on separate spindles, and so on.

If you only have one disk the difference may not be noticeable.

You may also take a look at Using Files and Filegroups from Microsoft.

With SSDs, it depends on your array config and class of the storage. SSDs have no more throughput but lower latency, so you should do some performance testing first, and see if is good enough to satisfy SLA with your production workload. At the end of the day, only thorough performance tests can clear your doubts.