Seedlings I have grown start producing a very limited quantity of nuts 10-15 years after planting. The quantity increases each year. My climate is a cool coastal one with day temps in the mid 70s, nights in low 40s during our summers. Many do produce good nuts (they are macadamias!), just a few have nuts with an opening in the shell, or a deformity of some type. Still, most seedlings produce good nuts, just takes a long time. Grafted ones are quicker and nut quality is predictable. All my trees produce, eventually. I have Cate, since it is a commercial variety, but for me, it is a poor producer, average sized, nothing special. Again, our climate is very different from the San Diego area where Cate is commonly grown. I only have one Cate for comparisons. Here, there are far better varieties. I have 12 grafted producing trees (some duplicates) and 26 seedlings, most producing various quantities based upon age. Seedlings were planted after grafted ones. Many of the macadamias have approx 12 in trunk caliper and are on drip irrigation, fertilized yearly with rainfall.
If I were to pick a variety to grow here, it would be Beumont. HAES 752, and HAES 747 are good. Z-3 has the sweetest nuts and the largest (that may not be crackout size). Several seedlings also have large nuts.
In our climate the trees grow like weeds, only pests are the tree rats. Not bothered by frost now, newly planted trees were killed by frosts (no freezes happening in recent years).