For heavily seasoned stuff like tacos, I find ground turkey to be much closer to ground beef (and easier to prepare) than impossible meat.
Impossible doesn't audit or disclose their carbon footprint, but it has been estimated to be a 90% reduction from beef. It turns out switching to turkey also produces a 90% reduction, and is much cheaper:
https://www.bbc.com/future/article/20220429-the-climate-bene...
The article I just linked is excellent. It also has data on climate emissions from transportation and refrigeration for different food types (transportation is a tiny factor for most foods; refrigeration is a larger factor than I realized) and data on emissions from food waste.
Tl;Dr: buy rapidly perishable goods locally; don't bother with things that have a long shelf life. Avoid beef and other ruminants. Don't waste food.
That last point is a big deal for us, as we feed scraps to the chickens, and doing so reduces our emissions way more than I realized (rotting food has very high emissions).