TMX has the potential for remarkable sharpness. But more than any film I've tested, it reveals a developer's bias toward sharp grain vs. soft grain; any tendency a developer has toward softening grain will give an image that looks diffused. So the recommendations you've gotten that achieve particularly sharp grain (Rodinal 1:100, or Rodinal with sodium ascorbate, D-76 1:3, FX-1 or FX-2) will give you the sharpness you are looking for.(posted 8194 days ago)Tanning developers are ideally suited to this end. I've only very limited experience with TMX in PMK, but you might look for some feedback with this combination. It should be a very sharp match.
I've used catechol based developers extensively with TMX and have found nothing reveals as satisfying a combination of fine grain and high sharpness. DiXactol, Pyrocat-HD, Jorge's catechol formula and my own formula all work great with TMX. The great thing about tanning/staining developers is the stain fills the gaps between grain particles and smooths the tonality, thereby producing the high acutance, etched look of Rodinal without the attendant graininess. For the highest sharpness with fine grain, nothing I've ever seen rivals a well formulated catechol or pyro developer.
With that said, however, if you want something less toxic and easier to use, check out Pat Gainer's vit-c developers (see unblinkingeye.com). I've found his formula the best non-tanning developer for sharpness, fine grain and tonality. I've slightly modified his formula so I can use it as an A+B type (which keeps better and permits adjusting ratios for contrast control) as follows: A - 8.0g ascorbic acid, 0.8g metol + 500ml distilled water; B - 6.8g sodium hydroxide, 24.4g borox + 500ml distilled water (note: Pat has told me he now uses 10% sodium metaborate as his B component.) I use this developer 1:1:14 @ 70, TMX @ 11 min, Delta 100 9 min, Acros 10 min.