Richard, you will find Neopan 400 has less slightly grain than Tri-X but there is not much between the two. Neopan-400 also needs a bit of a boost in shadow detail, so exposing at 200 is normal for me, but I have run at 800 souped in ID11 1:1 with great results too. It is my go to 400 speed film most of the time.
Tonality wise, Neopan-400 is on par with Tri-X. Lovely glowing highlights and decent shadow rendering. Most of the time, I soup mine in Pyrocat HD and have had long subject brightness scenes rendered very well with really good tonal seperation. Similarly, with lower light conditions, it does well and the tones seperate out nicely. Like I mentioned before, it does need more exposure for shadow detail though.
As for being visually sharper than Tri-X at 5x7 enlargements. I would say that it would be hard to see a discernible difference at that small a size. Maybe if enlarged to 14x11, that would be easier to see, but even then it's likely nothing to sweat over. I think from a price perspective. It is the best value film for the money being so much cheaper than either Kodak and Ilford counterparts. Where I get my supplies from anyway, and every little savings helps get other needed consumable materials.
Try it, I think you will be pleasantly surprised.