You don't need a RIP to get neutral B&W; a good custom profile will do that. If you're not getting neutral grays in the lighting the profile was made for, then the profile is bad. The primary benefit of a RIP is the better ink linearization and reduction in the amount of tweaking the profile must do.
Yes. For one combination of ink and paper. Under one lighting condition. Grayscale images with the Epson 2200 do evidence metamerism. The profiles that are available for IP Lite compensate for different lighting conditions.
By the time you buy a half dozen custom profiles, you have pretty much paid for IP Lite. And you do not have the hassle of printing test targets, mailing them, etc.
IP also gives you other print management features that may or may not be important to you. It prints in the background, releasing the PC much faster. You can precisely place images, even multiple images, on the page and have tem print correctly. PS is not a print management program and its print management capabilities are very limited. IP has a lot more to offer in that regard.
I don't beta test for Colorbyte or have any financial or professional interest in them or IP Lite. I am just a customer who fusses about the UI but loves the result I get with my Epson 2200. Before I used IP Lite, I used to spend a lot of time tweaking my output to get neutral grayscale images. Now I do not.