I inherited a large crockpot form my grandmother that I mainly used for stocks and soups. I recently bought a basic 1.5qt oval that is perfect for meals for 1 or 2 for when I want minimal leftovers. The oval shape in more versatile than the round because you can put longer cuts of meat in there such as chicken thighs or breasts yet still have the correct ratio of meat to liquid. For the timing function, I just use a manual plug-in timer.
I don't have much experience with cooking actual meals in slow cookers, but so far my go-to dishes are braising dishes such as Lebanese Tahini meatballs a la Ottolenghi, Cuban Chicken and some Indian stews.
However I usually prefer using my pressure cooker for larger cuts and more versatility.
^ on the oval shape. I cooked a swiss steak meal for 4 for Sunday lunch and my 5 Qt is oval - handles a long cut with ease. Good shape for a whole chicken too.