You are a professional stills photographer, but maybe you are not yet ready to sell "movies" to your clients yet.
Why not employ a professional editor to do this part of this project, you can learn from him / her while you also study up the process and workflow.
Meantime...trying to help...
You choose an export setting to meet the requirements of the delivery:.
Bluray, DVD, Youtube and Facebook. (These are where the clients want) all at 1080p.
Your clients are asking for the above which is actually 4 different encodes because they are 4 very different "deliveries".
Find out the deliverable requirement of each and then through trial and error... encode the project to each.
eg Youtube > H.264 (Youtube Preset)
Believe me... the learning curve on this, is a bit trial and error ( quality and file size, streaming and upload factors)
BTW: I have been doing this for a long time and encoding to client requirements is probably the least profitable part of my business. Its difficult to charge enough for the hassle of it all. Clients never believe how hard it is to get a 2 GB file down to a 4-5mb emailable file with qualaity to their expectation !.
The best self help is product's help file (f1).. You'll find the workflow described pretty well for everything..
Next best place to find tutorial and self help is adobe tv.
Here's what i found something you wanted:
Hope it helps