Levy, Jack S. (June 1998). "The Causes of War and the Conditions of Peace". Annual Review of Political Science. 1: 139–65. doi:10.1146/annurev.polisci.1.1.139

...even if you don't read a lot of academic papers.

There's 'hegemonic stability theory' and 'balance of power theory'. The first says unipolar is more peaceful (think Pax Romana, Pax Mongolica, Pax Americana), and the second says multipolar is more peaceful.

Levy says that two regional powers of similar strength are less likely to go to war when the globe is dominated by a single power.

"The dyadic-level “power preponderance” hypothesis, which holds that war is least likely when one state has a preponderance of power over another and is most likely when there is an equality of power, has received widespread support in the empirical literature (Kugler & Lemke 1996)."

Bremer SA. 1992. Dangerous dyads: conditions affecting the likelihood of interstate war, 1816–1965. J. Confl. Resolut. 36:309–41, https://sci-hub.se/10.2307/174478 supports balance-of-power theory: "After reviewing the empirical literature on dyadic power and war, Sullivan concludes that "though the findings do not speak with one voice, a tendency seems to be, with some certain exceptions, that situations of preponderance are more likely associated with nonwar than the opposite"(1990, 129), an assessment with which I essentially agree" (See also the 0.36 number for large power differences in the paper's results table). Though note that that study looks at pairs of countries, not at geopolitcal superpower structures. This contradicts the Levy paper which says "there is substantial evidence that at the dyadic level an equality of capabilities is significantly more likely to lead to war than is than is a preponderance of power (Kugler & Lemke 1996)"

TL;DR academics disagree on whether unipolar or balance-of-power leads to more war