Hi June
The flavour is different. Anyway, Yes can leave it one Slow (min) all day, safe also. or there is a max meaning standard cooking for casseroles (possible 2 hours) You need to quick fry the meat & veg first, to seal the flavour, which defeats the object. Otherwise the veg will not cook properly. Also the veg needs to be placed on bottom & meat on top.
Hope this is useful
ps. I use a Pressure Cooker myself and it's fantastixc. 15 min for veg!!, also energy efficient cuts down 1/3 cooking time approx.