I bought the 3 pack of waist high "control" knickers from Primark to wear under some tight white trousers (don't judge me). They sell them in 3 packs in plain white, plain black, and possibly flesh coloured too.
I'm addicted. They're stretchy and so so comfortable. They aren't tight or Spanxy at all (to my mind they don't control anything at all) - I am a size 8/10 on the bottom and wear a S (there is also XS) which is very slightly loose, which I prefer. The shape is not as large as a full brief, rather like bikini bottoms with an additional part that comes up to the belly button.
I have now bought 9 white pairs and 9 black, and am rarely out of them as they are just so comfortable. I bought the first pack 2 summers ago followed immediately by the rest so they're 2 years old and have washed well, not lost their elasticity. The white ones are still a clean white colour and I don't use Vanish or vinegar etc. or pre-soak.
They are described as control pants but really don't feel like they are. Just super super comfy. And inexpensive.