Jimmy Rey posted a massive HD Remix wrap up post with a ton of interesting details on the game. A couple excerpts from the post that I wasn't clear on until now. Check it out:
Dipswitches. The Dreamcast version has several secret dipswitches for turning bug fixes on and off. We took the dipswitches that actually affect gameplay and put them in a menu for you to adjust, if you want. These only affect offline matches, so you can’t use them online. Note that the default setting for many of these is for a given bug to be fixed in Remixed mode but still unfixed in Classic mode (have to stay true to the original!).
Advanced networking. The delays in this project gave us a chance to experiment with several different networking techniques and we chose the best. We went with a predictive/rollback system that has the advantage of reducing input delay. I know that sounds pretty jargon-filled, so in plain English, it makes the game feel responsive and look smooth, even during lag. We were able to refine this from the feedback on our open beta test, and also from a few experimental things we tried in the patch to the open beta.
The final version of the game has another feature called “smoothing” that lets you turn the input delay up or down. We found that best results were when there’s a very small input delay of 2 frames.It’s a small delay that is still responsive, but can help mask network lag.But you can set this to suit your own tastes.