We know when Kawaki’s dojutsu increased to 4 lines he was able to use the Cubes, and pillars that even jigen wasn’t able to. And we know Jigen couldn’t fully shrink the flames Koji used but Isshiki who had 8 lines in his eye was easily able to. Meaning the evolved Dojutsu does increase the control, power and possibly the speed.
I think Kawaki/Isshiki both have the Full Power of the Daikokuten/Sukunahikona and the speed does increase. As well as the control. But as the manga progresses we will get answers