Thank you everyone for your taking the time to help!
To clarify:
I am the only user of these devices.
I prefer having them all signed into the same ID because this way all my devices can be seen in one place under Find My iPhone/ iPad/ Mac http://www.apple.com/icloud/find-my-iphone.html and also under Devices in Apple ID https://appleid.apple.com/
This way I don't have to manage, sign-into and sign-out of numerous different Apple IDs.
That being said, for the iPhones, I need each to be independent when it comes to iMessage/ texting.
I have iMessage turned-off on the iPhone 4S but it is enable on all my other devices.
I have different phone numbers for work and if I text a client from one phone, I don't want that person to see my Apple ID or the other phone numbers associated with my Apple ID and iMessage, only the phone number of the iPhone I texted from.
This is the part I was not sure about:
On my work phone iPhone 6 # 2 this is how things look
Settings > Message > Send & Receive
You can be reached by iMessage at
✓ XXX-XXX-1234 (iPhone 6)
✓ XXX-XXX-9999 (iPhone 6 # 2) grayed out - cannot deselect
✓ myemail@address.com (Apple ID)
Start new conversation from
XXX-XXX-1234
✓ XXX-XXX-9999
myemail@address.com
Based on what everyone wrote, it sounds like the settings for iMessage on a particular device using an Apple ID common to several devices are just for that device in particular and they are not "global"/ implemented on the other devices. This is great.
If I wanted to received iMessages sent to one device, e.g: XXX-XXX-1234 (iPhone 6) on another one of my devices e.g: myemail@address.com (Apple ID used on rMBP), then on the rMBP, I would select XXX-XXX-1234 also.
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Op, what is your objective? Personally I have I messages sent from my Apple ID since I change SIMs when traveling. This way people aren't getting messages from numbers they don't recognize. But what are you trying to do?
This is a great point. I do swap SIMs when traveling as well.
I really look forward to Apple coming out with a dual SIM phone. I know... not holding by breath.
I looked and looked on the Android side just recently: it has so many great dual-SIM and now triple-SIM models (I used Nexus phones concurrently with iOS for years and gave up) but I just can't trust Google and the Apps on Android with all the permissions most of them require when their core function don't even require them (yes, I know some can be denied within the OS after installing).
Per device, you can choose from which Apple Id identifier that device receives messages for.
[...]
Indeed, so it seems. Thank you for clarifying and confirming this.
2 people, 2 AppleID's. Everything else will cause trouble at some point.
If you need to share stuff, use Family Sharing.
I have never used Family Sharing. Will look. Thank you.
I'm sure if does work for you. But it definitely would not scale very well. And if you ever have an issue with that Apple ID, it affects your whole group. And it makes it hard for one of you to choose a different send from. And new devices will default to receiving from all identifiers. But that's somewhat OT from original post. Glad it's working!
A set up with the same Apple ID for several devices does create a lot of possible combinations and permutations!
My wife and I have the same apple ID. We both use iMessage without any problems. The trick is to NOT use your apple ID for iMessages. Under the settings page for messages, click on the "Send&Receive" button. At the top of the screen you need to sign out of your apple ID. Once you've both done that, iMessages will ONLY be tied to your phone number. When you're done signing out, you will have a new button that says "Use your Apple ID for iMessage". Just leave it like that and you will be fine... Note that you may have to re-apply this setting when you do major upgrades or get a new phone, because it is NOT the default setting.
I thought it wasn't possible to use iMessage without being signed-in.