FDM, particularly industrial FDM like running on a Stratasys Fortus, will be the best plastic 3D printing process to mitigate warping. I recommend exploring materials like ASA and polycarbonate for large, broad, flat parts. Avoid "warpy" plastics like nylon or ULTEM unless absolutely necessary.

FDM is better than SLS or MJF because the parts are built attached to a flat build plate. SLS and MJF do not have any supporting structures so broad parts can twist or flex during cooling. The sacrifice is in detail resolution. Maybe you could explore a hybrid approach in your design or splitting and assembling to achieve your results.