You might try seeds grown in regions that are often cool, cloudy or rainy, if you want plants acclimatized to less light. They seem to do pretty well in the shade in my area, but maybe not so well in the sun. Victory Seeds, Territorial Seed, Adaptive Seeds and maybe others might be good choices, if you can get seeds from them in your location. Some varieties may be from third parties grown elsewhere, though (e.g. the Neapolitan pepper at Victory Seeds).
I've said some recommendations in other places here, but I might recommend the following, depending on if they work well in your area:
- Ring of Fire pepper
- Grandpa's Home pepper
- Shark Fin Melon
- Bunching onions, shallots, chives
- Russian tarragon
- Ground cherries
The amount of foliage doesn't seem to me to be what matters. I think it's more of a matter of how used to the low light they are, especially over a period of generations. You should get somewhat better results if you save seeds and plant them in the same conditions (especially if you do it more than once), unless they're already quite used to them.
Generally, I think how much space they have is a bigger issue for tomatoes than how much light they have, but the right variety or seeds may help. Crowded tomatoes in the shade aren't a good idea at all. (Crowded tomatoes in full sun isn't nearly as bad, but still not ideal for most situations.) I've tried growing crowded, shaded tomatoes on two separate years with very few fruits both times. I gave some Oroma tomatoes from Territorial Seed more space, in the shade, and they did very well by comparison, and better than the Oroma plant I put in full sun (granted it was in clay-type soil; so that may have been an issue). Oroma has nice big leaves in the shade (the non-shaded plant had smaller leaves, I think). I got more tomatoes on the shaded plants. I doubt that would be the case for every variety, though.
Blackberries can do pretty well without lots of sun (you do want some sun, if possible, though), but they taste a lot better with more, in my opinion. They still taste good with less light, though. There's a big difference between some kinds of shade. You'll want it to be light enough that pollinators will still come, if possible, and you may want to give your plants more phosphorus.
Make sure not to neglect your soil just because it's in the shade. Amending it with compost and such should help.
The soil you use will make a big difference, also.