Many folk in the hobby don’t particularly like horn-hook couplers and often can’t wait to replace them with knuckle couplers. The view of many is that knuckle couplers are more realistic and they work really well with magnetic uncouplers.
Converting to knuckle couplers takes time and some effort and patience. If you are going to do this it is best to convert your rolling stock one at a time. Some mix them in consists until they are all eventually converted.
Regardless of what train couplers you use, they need to be mounted at the right height for them to work correctly.
If a coupler is sitting too high, then you can lower the coupler by inserting a shim between the bottom (of the car floor) and the coupler pocket. If, on the other hand, the coupler is too low, then you can add a washer (or two) between the truck and the car base.
You might have to replace the truck assembly (or the wheels), if the coupler is mounted on the truck, particularly so when a coupler is too low. My last tip is to buy a coupler height gauge – very handy!