Something I've wondered for awhile when watching Geoff Lawton's inspiring videos is where is he getting the stock for all these tree's he is planting? He shows video of mango, avocado, jack fruit, etc. Are these grafted or is he starting from seed and rolling the dice? I imagine he's grafting but how does he handle that task on his scale? He has something like 40 acres if I remember right.
I'm pretty sure that at this point he starts almost everything from seed or clonal root stock that he gets on site at multiple the farms/institutes that he's connected with all over the world. I'm also pretty sure that people try to give him as many things to try as possible. I've seen many videos of the propagation areas on his land and there does seem to be quite a lot of diversity. Once you find out what works best in your area, then all you have to do is keep propagating those species and spreading them around. Keep the winners and remove the others. Nature usually does most of the culling anyway.
In my own practices, I strive for as much diversity as possible. For instance, I plant hundreds of oaks and apples every year. As they grow, I make decisions about which ones to keep and then I cut out anything that isn't desirable. Some plants have a lot of genetic diversity and so you'll have to cull quite a lot of plants while others are almost true to form with the parent plant and can be more reliable in their performance.
You can also order seed or root stock in bulk or wholesale which cuts the price significantly. Starting with tree seeds is a lot less expensive than buying in 2-3 year old saplings, but you'll probably lose a lot of seedlings and also have to wait longer for them to fruit. It's a good way to deal with large pieces of raw land where you won't have time to baby things too much. If you only have a small backyard, I would recommend buying older trees and spending more time taking care of them.
I'm pretty sure that Geoff and his team have figured out what works and they go with that for the most part. They probably have smaller spaces dedicated to trying new varieties of plants and animals, but I think he's really focused on making the most of the space and not necessarily looking to have a large number of exotic stuff just to say that he does.