We study 3-jet event topologies in proton-proton collisions at a centre-of-mass energy of Formula omitted in a configuration, where one jet is present in the central pseudorapidity region ( Formula omitted) while two other jets are in a more forward (same hemisphere) area ( Formula omitted). We compare various parton level predictions using: collinear factorisation, Formula omitted-factorisation with fully off-shell matrix elements and the hybrid framework. We study the influence of different parton distribution functions, initial state radiation, final state radiation, and hadronisation. We focus on differential cross sections as a function of azimuthal angle difference between the leading dijet system and the third jet, which is found to have excellent sensitivity to the physical effects under study.