Proxy Media: Transcode Source File and Export Read File...

Hello, I'm new to FCPX. I have a Panasonic HC-X920. When I shoot things I copy the entire folder tree to my hard drive and import from there, rather than directly from the SD card.

I learned that FCPX "re-wraps" the truly original h.264 MTS files to "Original" h.264 MOV files. Not a huge deal, as there doesn't appear to be quality loss, and the MB/s rate is slightly higher on the MOVs. Ideally I'd be able to use the MTS files but FCP is Quicktime-based and I've decided I'm not worried about it.

Anyway,

My computer can't handle playing back 1080p 60fps h.264 footage. In order to have playback on an FCPX timeline, I have to transcode to either Proxy or Optimized media. Optimized, of course, takes up a ton of space, so I'm curious about using Proxy. But I want more info first.

I'm most curious about question #1, but here are two questions:

1.

Let's say I transcode everything to Proxy Media upon import. When I go to share/export a final file from my timeline, which of the following does FCPX do?

(A) Export the timeline using/reading from the lower-quality Proxy media, ignoring the Originals.

(B) Automatically replace the Proxy media with the Original media files, and export the timeline using/reading the Original media files while ignoring the Proxies.

(And if B is the answer, is it reading the Original MTS or Original MOV? I'd assume MOV, right?)

Does this question make sense?

I'll mostly be editing home movies with this, so it's not imperative that I be able to see what I'm editing in vivid detail and I can use Proxy for that to save disk space. But I DON'T want my final exports to be based on that lower-quality transcoded 422 Proxy Media; I want the proxies to be view-only, and I want the final exported quality to be based on the quality of the Original media.

My other question:

2. (probably not a big deal either way)

When FCPX transcodes to Proxy and/or Optimized, is it reading from (A) the "Original" MOV files it created upon import, or (B) from the "truly original" MTS files?

Thanks!