Is there any explanation on how Z fighters control the power of their ki based attacks?
I do not think they are any in-universe explanations for that. I have actually noticed some inconsistency in the damages the Z fighters can generate when fighting.

However, it is important to note that Dragon Ball is an old Shonen manga (first chapter was released in 1984). Back then, authors were not so rigorous and consistent with the plots and power levels as in other more recent mangas. Akira Toriyama regularly (and casually!) admits he has introduced many plot-holes in the Dragon Ball series. 

On a side note, when Goku defeats Frieza, he is about 150,000 times stronger than when he fought Raditz. How much stronger is Goku in Super Saiyan Blue form? I reckon it can be difficult to be consistent when such exponential strength growths are involved. 

From the latest Dragon Ball Super episodes, I suppose it is safe to say Akira Toriyama has not changed his approach to mangas and does not pay much attention to such minor inconsistencies.