I don't believe 10 billion for one second. Not even if they were all "living in caves", chucking spears and eating leaves only. We're so far into overshoot it's not funny. At the current, global average level of consumption we need almost two Earths to provide the energy and materials—and absorb and process the pollution—to sustain it. For a society like the US, spread all over the world? Five Earths. The few (like three) societies with the lowest ecological footprint (yes, that's a thing) are tiny and very rural. If we're lucky, a big if, our future, although it's likely a process that will take two to three centuries in all, will look like 18th century New England. "That which is unsustainable will eventually no longer be sustained."
Improvements in technology bring improvements in quality of life. Technology improves more rapidly with a larger population. Larger populations mean fewer resources (including personal space) per capita, which decreases quality of life. Hence the trade off; somewhere there is an optimal balance although I expect everyone will have a different view of what that would be. The absolute number of people who could be physically squeezed on to this planet and kept alive in some basic manner is probably huge, well in excess of 10B... but what quality of life would a population of that size have?
Oh well humans are going to change everything about the earth, that is a given. But if we are looking for some kind of ecological balance based on nature we are well beyond that in terms of population and consumption.
Then stop consuming Ricter. You have that within your power. If it is such a problem to you, stop consuming and drawing down the natural capital. Ohh let me guess. You wont. You want everyone else to make sacrifices while you go along your merry little way. Typical boomer behavior.