Well it looks like none of that will be necessary as the brightness with the aluminum emitter from Amazon looks perfect to me, at full strength@FixIt the front door light strips aren't connected to a light pipe extension like the aftermarket add-ons. The LED is right at the tip of the light strip molded in. Practically required surgery to get it out, and then you'll have to somehow get your new LED to sit exactly flush with the end of it.
If it turns out the rears are much brighter than the factory ones your best bet is going to be to do something to dim the rears down to match.
I still need to find a good cable to tie into and I probably end up routing a cable from the door controller to the dash (sigh), since I did not find a useful cable in the bundle behind the glovebox. Here are a few pics on how it looks. The first picture shows where I drilled a small hole for routing the small fiber that is attached to the AliExpress strip. It worked out just fine.