Dvds need to be playable to interlaced sets, so even though they are stored as solid frames, the hardware will think of them as if they were two interlaced fields stored together, sortof. Which is kinda confusing.
1) Uhhhhh....
2) Computer monitors are normally run progressive. So, you'd want to playing both fields as one frame. And your player cooperativly does that. But you'd still be going one line at a time. Playing the wrong field first means that line 2 goes at the top, line 1 below that, 4, 3, 6...
So that part actually makes sense to me.
3) That's weird.
I don't get the scrambled picture. I would think maybe ripping them and fixing GOP errors, like in ADM's editing guide might fix it. But you say changing it in Premier worked. I don't know if you need to fix GOP errors if you convert VOBs in TMPGEnc, anyway.
Are you usually working in NTSC? Maybe that's the difference. NTSC generates extra frames-per-second by duplicating fields. That takes 24 fps and fakes the framerate up to 30, that makes little pauses. Pal just speeds it up from 24 fps to 25 fps. (Both methods suck). But if you normally watch & work in NTSC, you wouldn't really notice that.
Hmmm... Maybe top field first is the wrong setting in TMPGEnc, and Premier is fixing it? But that still doesn't explain #3, unless, like I say, you're used to NTSC.
On the other hand, are you sure your PAL source doesn't have interlacing in it? Sometimes happens if they convert from NTSC to PAL. (It shouldn't be that way, anymore, ever, but it still happens). I'm about to go look up a thing that'd tell you. I'll get back to you in a day or two (or...), if no one comes along with better answers.
Hope I'm not wasting your time, in the meanwhile.
You did say "any information", right?