Montreal-NJ-Memphis-Dallas-Montreal is roughly 3800 miles over the quickest route and will take you roughly 70 hours to drive. This includes time for extremely short fuel/food/bio breaks. No sight-seeing/exploring time. Over 14 days, this means you would average 5 hours driving per day. This leaves you plenty of time to explore, meander, and go a bit off the main path to see what's out there.

If you add in a side trip to SLC, it's roughly 5600 miles, about 102 hours with the same quick fuel/food/bio breaks. Over 14 days, this is about 7.5 hours of driving each day. You could still explore a bit but your time will be more limited to do so. Exploring off your main route will be tougher to squeeze in.

So, like I said in my last post, it all depends on how much of your time you want to spend driving and how much you want to spend exploring and just letting your muse be your guide. Only you can really answer that.

Also, you might very well find that keeping up this pace day-in/day-out, even for only 14 days, gets quite tiring and that you might want at least one, if not two, days where you're not on the road at all. Maybe more depending on what you find to explore along the way.

Also be aware that at this time of year, weather could get in the way of the best laid plans. A storm front could sweep in making travel take longer. In severe conditions, it might even mean a layover for a day or so until roads clear.

This is the best answer I can give you. It's your call.