I suggest that you install your programs in their default locations, specified in the installer. I installed Photoshop first, and then I installed Lightroom. Lightroom automatically chose Photoshop to be my external editor, and everything worked fine.
No suggestions here about using an SSD. I don't have one, and haven't felt the need for one. If your computer handles Lightroom properly it shouldn't matter. I purchased a basic off the shelf HP Computer, 8 GB ram, two hard drives, integrated video/audio, nothing special, no attempt to purchase a "super speed high performance" computer. It handles Lightroom and Photoshop without any problems at all. So performance really depends on whether or not your computer is fully compatible with itself. From the reading I have done in various forums, it seems to me that the ones having problems with Lightroom are the ones who try to customize their computer in order to make it a screaming machine for Lightroom. I might be wrong.