The storage I had in mind was: SSD for responsiveness of the operating system and other main programs. As I assume most non-profits don't want to spend time/hassle upgrading down the line, an SSD ensures the best user experience for years to come (and as operating systems and other programs only become more demanding). The 1tb drive is for media, and my experience is that churches tend to produce a lot more media (especially if this is for presentations) over 4-5 years than you'd think. The 2tb drive is simply to back up the other two, so everything can be easily restored if something bad happens.
The card you listed is certainly acceptable, and the other is just the updated version of it. The video memory in your use case is not worth considering.
As for OS, I'd highly recommend going with a clean install of Win10 off the bat. Microsoft will eventually phase out support for Win7 and force you to upgrade anyway at some point during the computer's life, and most of the Win10 issues I have encountered have all been on upgraded systems. Again, with ongoing maintenance and support being important to keep to a minimum.....I'd go with the most recent OS on offer to ensure the best user experience over time.