I’m not a fan of story points. Because they’re numbers, there is always the temptation to try and turn them into hours or days or fractions of a sprint. Plus you frequently have to re-explain your scheme (Fibonacci? Doubling? Custom?). T-shirt sizing is a little better, but what does “size” mean? If it’s time, then you’ve baselined against hours or days. Or is it effort? Or riskiness?
When planning work, the questions usually boil down to “what can we get done quickly” and “what it going to take a while”. Sprints are filled to capacity, but so are stomachs. Instead of saying “we can produce 24 story points”, think instead of “we can cook 8 hot dogs, six burgers, two steaks and a rack of ribs”, or “we can only get one Freddy Flintstone rack of ribs done”. In short, you’re not planning sprints anymore, you’re planning tailgate parties.
When it comes time to plan a sprint, your work in progress is determined by how big your grill is. Are you a small time, like about the size of a tailgate hibachi, or are you a larger high-performing team and your grill is huge, like the fireman’s barbecue? Regardless, your work-in-progress is confined to the cook surface. You can probably fit 3-4 hot dogs, or 2 burgers, in the space of one steak. You can’t fit Freddy Flintstone ribs on a tailgate hibachi. It’s all relative.