Your question may be too ideal, and if you don't concern power, area, opamp speed, just increase your OSR to very large is ok or just increase your filter to very high order is ok? You don't need to consider speed, so why don't use very high OSR? you don't care about the power and area, so why don't you use high order?
Block level investigation is to search some topology that best meet the practical design specs such as power, area, speed, noise, etc. So you must consider these aspects before you choose what OSR and what order.