I can help with a couple questions, but you may want to check the fertigation section for ez flow specific questions.
Normally the RP needs to be installed horizontal. There are some that are able to be installed vertically, but it needs to be in the specifications. And as a backflow tester, normally if I see a vertical install it is a mistake on the plumber's part because they are generally Specified for flow down only. For your project, It is probably not practical to install vertical, but you may have time to search for a flow up, I have not come across it yet.
For the drip zones, get the Valve assembly that comes with filter and pressure regulating in all in one package. Normally pre-installed, it helps not to install the components backwards. I know following arrows should not be that hard, but.
Good luck with the project. Usually you will have a 3/4 option or 1" option on the valves for drip. If your flow is below 10 GPH go with 3/4. I normally use that as a cut off. Some other contractors that do more drip than I do may use a different cut off point to move the 1" valves.