Started following this thread as I also have an Instant Pot. The pressure cooker and the slow cooker are two different modes, it doesn't have some way to do both at once although you can easily switch from say pressure cooking to then slow cooking without removing the lid, but I'm not aware of any recipe calling for that.
The main difference between an IP and any other slow cooker or casserole is that it has exceptionally low vapour leakage, so whatever liquid you put in at the start will not boil off (and may significantly increase in volume depending on what else you put in there). I find this tends to make a lot of traditional slow cooker recipes come out with far too much liquid, especially if it's a stew that includes the exact amount of thickener for the expected amount of liquid. In some cases you can adjust the recipe by adding less liquid, but sometimes that results in not enough liquid for the cooking process itself. So while the IP is great, that aspect can be annoying. I've had quite a few things come out badly, although usually that only happens when my plans change and I increase the cooking time. While very long slow cooking at low temperature can work well, it's also certainly possible to over-cook things.
I've tried making bolognese in the IP a couple of times, which is something I am generally pretty good at making on a traditional cooker, since it was the first thing I learned to cook. I make my own variation based on the Accademia Italiana della Cucina recipe and Delia Smith's recipe (which is the best I've found, even if it's not quite the "classic" version). I normally leave it to reduce overnight in the oven, which gives amazing results. Trying to do the same thing in the IP just doesn't work because it doesn't reduce and it tends to end up gritty (overcooked).
All that said, someone mentioned the holy grail notion of just chucking a bunch of leftovers in the slow cooker in the morning and coming home to a decent meal in the evening with minimal prep. That certainly is possible with the IP. Once you get to know the approximate ratios that work, you can certainly get away with this. I've done it successfully a few times. Other attempts have gone badly, usually when I've tried to use a meat that wasn't robust enough for all-day cooking. It's worth keeping notes about what works and what doesn't, experimenting when you don't mind it going a bit wrong and otherwise sticking to something you know is going to work. Just don't complicate things by trying to add ingredients with different cooking times that otherwise need to be added at the end. You can also save time by not browning meats: it most cases the only difference it makes is cosmetic.
There are quite a lot of dedicated IP recipes out there so it's definitely best to start with those rather than trying to adjust others until you get used to it.