for my new grow, I'm curious now that I have ...

You really can't tell anything... look at it this way - if you have two seeds and one of them cracks open and sends out a taproot on Sunday morning at 8am and the other one doesn't crack open until Sunday at 4pm - well, seed #1 has a 8 hour head start on growing the tap root and will always be bigger ... so my short answer is "no" - doesn't indicate anything at all.... Good luck!

I have never read any research that shows a longer tap root produces a bigger plant or higher yield. One problem is the actual time of the germination. You may start many seeds at the same time but the actual germination may occur over a period of days. So, the bigger tap root may simply be older.

From my experience this will always be most vigorous plant, but doesn't mean it will yield the most.

I've personally never heard of the taproot itself having any determination on how big the plant will become. That said you are right in thinking bigger roots, bigger plant. I always grow in 20 litre pots for that reason, root stims also are essential.