Typical of most “scientific studies” the clause, more research is needed to prove our study, is ubiquitous and obviously a plea for more funding. When is enough data gathering or funding enough?
… “More research is needed” is not only a “plea” for more funding, it is also a “plea” to be able to continue the collection of more data. So the answer to your question for both is that there is never enough of either because the goal is not to answer any question. Notice that in many cases the Predesignation of the Question prior to inquiry, if in fact there is even any attempt to do so, is always extremely vague. This is a direct violation of the correct process and application of The Scientific Method (Problem - Hypothesis - Test is the most basic formulation). You can’t begin inquiry and the collection of data and then, after the fact, decide on “your question”.
There is a lot going on in the background…