Minato's feats of warping very large objects & too many people at once clearly shows he had extremely large Chakra reserves & unlike Jiraiya he doesn't need elder toads tt enter SM due to his supreme Chakra control which enable him to balance nature energy better than Jiraiya thus making him a perfect sage...but he can't maintain the mode for long due to his lack of practice.
Hiruzen never shown any large feats when he still alive
But he shown one large feat when he is an Edo(Counter Guruguru's shinsuusenju 5 elemantal attack)
As an Edo their chakra reserve is same like when they are alive and not limitless I think.
If Edo chakra is limitless sure Tobirama can make many clones while maintaining 4 Yang formation barrier. But he unable to created more clones.
From reason above, Alive Prime Hiruzen can perform same feat as Edo Hiruzen that required large chakra to done it. And it give you some clue about Hiruzen chakra reserve there.
And I assump Hiruzen chakra reserve is massive.
What do you think?