IFR training is by far the most miserable/demanding thing you can do in aviation. I did my training after work in the wintertime. It was 30 something degrees during my lessons and I always came out sweating. So what can you do to make it easier? Of course, fly the simplest airplane that will work. AKA Cessna 172. But sometimes that's not practical because of location, availability, etc. It's hard to imagine an airplane with more to do on an approach/go around than a 231. (I had one, loved it.) You are correct in your line of thinking that an O is easier. No turbo, no cowl flaps, no prop adjustment, (as long as it doesn't have the 2700 RPM STC). Everyone is knocking your instructor for making you do approaches. Assuming you already have some hood time, what else do you do on an IFR lesson? There is one thing that you can chisel in granite. Anybody who does their IFR training in an airplane more complex than a 172 is a better man than me.