Grain is basically built into the film. You can screw around with different developers with very little to show for it. So called fine grain developers have high solvent action that kills fine detail.
So quit fooling around. Options are bigger negative or slower film. Bigger neg is best.
TMax 100 is the finest cleanest easily available film. It works well with my scratch mix D76. The more you dilute the developer, the rougher the grain. If you use stock developer, and then use a stop bath, it works more like 1:1 dilution grain wise. SKIP STOP OR WATER RINSE AND GO STRAIGHT INTO FIX. The only downside is you kill the fix faster. Big deal. I never reuse it on important film anyway. I do use an alkaline fix so water or ss is of little value. In fact alkaline developer, acid fix, and alkaline fix seems silly to me.
The biggest surprise is you will get is over expose one stop and cut development 20%. Shortened time in developer seems to have a much bigger effect than changing developers. To compensate for short times, you need more exposure. The reverse, called pushing, does not work nearly as well if at all. You also get a beautiful tone range with lots of shadow detail and the prints are still sharp. I have tri x prints 6.75 x 10 where you have to look really hard to see the grain.