That said, though I'm not a T-grain fan myself, I think TMY seems like your best bet if you really need something that will work handheld while allowing you to stop down for appropriate depth of field. The difference in apparent grain between 35mm and 120 is there, of course, but less so in 645, and it sounds like you might still find Tri-X (or HP5) too grainy for your purposes. (Probably Fomapan 400 too; if anything it's a bit grainier.)
But basically, high speed and small grain are natural enemies, and you aren't going to really be able to optimize for both at once. You might find that TMY is a good compromise, with perhaps FP4 or TMX as a slower film for tripod use and bright conditions.