Video Conversion & iMac 27" 5k Display Settings?

Hi,
I'm about to pull the trigger on a maxed out iMac 27" 5k (Late 2015) along with a Pegasus2 R8 24TB in RAID 5 for 4k video editing. I have an enormous amount of 720 x 480 29fps and 1440 x 1080 29fps .avi video that I want to edit in FCPX. Please correct me if I'm wrong, I believe that I would need to convert the .avi to H.264 and then ProRes 422 within FCPX for the best quality. I have a few questions;
1) How well does FCPX deal with these formats?
2) Can FCPX convert my 720 x480 video to widescreen without degrading, etc.?
3) In regards to the 27" 5k retina display;
a) How well will the video display due to its lower resolution?
b) Will 720 x 480 and/or 1440 x 1080 be too pixelated or will the display settings correct this?
c) How good is the quality of older DVD's?
4) Any converter suggestions?

I know it's a lot of questions, but I would sincerely appreciate your experience along with any suggestions that you may have. As always, Thank You. Ray

You'd transcode .AVI to ProRes, no H.264 would be involved. And you's use Handbreak or MPEGStreamClip or something like that. Does Compressor read AVI? I think some of the AVI codecs it will read.

1) Great, in a compatible codec
2) Yes, transcoding to ProRes will not lose any image quality. But it isn't FCPX you'd do this with, but Compressor, probably.
3) Video will display just fine, but depends on what zoom level you're using. 100% will show the video at its native resolution, best you'll see it at. 100+% will begin to degrade and pixelate, the more you enlarge it. It has nothing to do with display settings, but the zoom amount you play it back at. An iMac display is a much larger resolution than your standard def video, so that video, at native resolution will be a smaller window, not full screen. Going full screen will degrade it. Just physics. The resolution of any DVD is standard definition. As for image quality, that depends on the image quality the original film or video was shot in, and the quality of the MPEG-2 transcending. But even the best quality back then, is not as good as today's digital HD and UHD flavors. So the question is, what is your target output frame size, and what delivery method?
4) Compressor, MPEGStreamClip, Handbreak, depends on what specifically you're doing. Rippling DVD's you have a legal right to rip from, MPEG StreamClip. But I'd be sure you have legal rights to use that video, or own that video off of those DVDs.

Thanks for the info...... Nice to know I can convert .avi straight to ProRes. I'll check out Handbreak and MPEGStreamClip for the conversion as well as how to use it. Is one any better than the other?
Glad to hear that the 5k display will give the proper quality of the mentioned formats.
As for delivery methods.... streaming and/or Blu-Ray DVD. If streaming, I want to output to the best quality FCPX will offer.
I also need to learn about Compressor and it's uses. Thanks again for your help. Ray

BenB wrote: You'd transcode .AVI to ProRes, no H.264 would be involved. And you's use Handbreak or MPEGStreamClip or something like that....

I have imported much .AVI DV material into FCPX without transcoding or pre-converting. That is NTSC, 720 x 480, 29.97, much from the old Panasonic AG-DVX100p, but also other cameras. Of course you can optionally transcode to ProRes (either Optimized or Proxy), either during or after import. However in some cases such as DV, the content cannot be optimized.

If the OP truly has an "enormous" amount of material, I would generally suggest not transcoding but import direct to FCPX using "leave files in place", then sort, keyword and organize the material.

On many projects only a small % of the original material is selected for the final product, so transcoding everything when 98% may not be used seems a waste of time and disk space.

It is unclear to me under what conditions (if any) transcoding to ProRes from .AVI helps image quality. I often see urgent statements that compressed content must be transcoded to ProRes, else color correction results will be suboptimal. However I do not recall ever seeing anyone methodically test this.

Thanks for the reply..... I was under the impression that .avi had to be converted for FCPX to accept. All I can say is "Awesome" due to not having to do so!! It would be nice to know if ProRes 422 would improve the quality, but it probably won't.
I have "at least" 500 hours of .avi, AVCHD and GoPro HD Hero2 .MP4 video. I now own the Sony PXW-X70 with the 4k upgrade.
In addition, I'm about to convert about 60 VHS videos into the H.264 format in which I understand FCPX will accept. Thanks again for the help, I sincerely appreciate it. Ray