All apps, I believe, use ffmpeg. They may take a bit longer…because it’s done over the network, time not needed removing the drive and taking your tablo off-line.
A couple have some commercial editing. Generally you may have to continue that as you’re doing. They all read tablo’s DB, so you do know what show you’re getting - that’s the greatest plus.
I’ve found capto, used along with wrapto - great for scripting and scheduling.
This isn’t exactly the same… but has some similarities, if you want files copied
Most/all these developers are still active in Tablo Community and others for assistance. Some are, kind of, still actively developed, as needed I guess.
There are post how to directly use ffmpeg with the playlist so, again, you don’t have to take your tablo offline disconnecting your drive.
You can automate the export process, so it’s irrelevant how long it takes in some cases, even schedule it. Processing time is often tied to your hardware. If storage space is crucial, you might consider looking into inexpensive reliable large capacity drives and storage devices.
The “resulting file” size will depend upon somewhat on the resolution and length of the original. 480i is going to be smaller than 1080p recording - depending on your maximum recording quality. (maximum does not equal recording are upscaled to the maximum setting)
If this disconnecting, multi-step… removing just the beginning and end (?) transcoding process works - great. If it ain’t broke don’t fix it 
I save every show I want, regardless of size. How long does it take, I don’t really pay attention any more, a couple minutes each 30min 720p show maybe.
My media player jumps in 30 seconds or 1 minute with a key tap - tap, tap, tap and I’m through a commercial in moments. (be nice to archive without commercials, but not the time investment for me)