My modern 2mm stuff I do in groups of 2-3 vehicles/guns or multiple infantry/weapons groups. I tend to use them for 1 base = 1 platoon/company/battalion type things. Some recce elements, tactical HQs, FOs etc are based as single vehicles on half size bases.
Spearhead sized 30mm x 30mm bases are fine for this sort of thing.
My Horse & Musket stuff is based on 30×15 for infantry (so two bases back to back tesselate nicely into a 30×30 element as an assault column, which can face backwards to ‘form square’ or stand side by side to ‘be in line’ and end-end for ‘march column) and 30x 20 for cavalry, guns etc. Some stuff, like Tercios and big pike blocks are on double size bases. Again, tactical HQs are on small bases, Army HQs on great big bases covered in tents, wagons etc.
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke