When doing a casserole type dish always add a lot less liquid than you think you need - slowcookers don't evaporate off liquid in the same way that other cooking method do. Slowcooking also works better with slightly fatty cuts of meat, lean meat doesn't cook the same way. Shoulder would be better than loin for slowcooking. If you buy lean meat to reduce your fat intake, don't for slowcooking. Instead make the dish in advance, let it cool and refrigerate overnight. Skim off the fat and reheat. The fat is needed for cooking, but by doing it this way you don't have to eat it.
With your loin steaks you could try frying off some onion in oil, put that in the bottom of the slowcooker (include the oil with the onion, the onion shouldn't be swimming in oil when you fry it off), put the loin steaks on top, some chopped apple and chopped carrot over the top of the steaks, some sage/mixed herbs, salt and pepper, and cook on High for 1-2 hours before dropping to Low for 4-6hrs. The apple should provide more than enough liquid to cook the steaks. If it does look dry a couple of hours into cooking you can add a very little boiling water from the kettle.
Given the choice, I would always go with shoulder (pork, lamb), chicken thighs (ideally cooked skin-on and bone-in for maximum flavour), or one of the really tough/cheap cuts that has bags of flavour but needs a long slow cook to become tender - beef shin, ox cheeks, oxtail. Tough sinewy meats are amazing done in the slowcooker, the sinews break down for amazing flavour and texture.
Not sure what to do with the wings, they never have enough meat on them for me to bother with. They would make a truly amazing chicken stock though. Slowcookers make the best stock. Wings, water (add from the kettle so the slowcooker doesn't have to spend 2 hours heating it), stock veg, and leave on Low all day. Pick off the meat afterwards, it won't have huge amounts of flavour but with the stock could make a great risotto.