Hi,
regarding to mesh resolution, why is it not good? What were your settings?
Also, regarding to reconstruction, what are your settings and PC parameters? How many inputs do you have ? Do you have enough space on your discs?
Regarding to PLY, do you have there some error message?
What were your export settings? Did you have set right coordinate system under Export Model/Export transformation settings as Project Output?
As you are using drone images in this project, did you see this tutorial series: https://www.youtube.com/watch?v=jxOCAr_33zA&t=21s