Q.pruning an old tall camellia
I have several old, tall camellias 15′ plus,, I’d like to get them down to about 6′ or 8′ as they now bloom almost out of sight. What is a safe way to do this? How extreme can I be?

Overgrown camellias can be rejuvenation pruned (severely pruned) in late winter or very early spring. You can remove 1/3 to 1/2 of the camellia's overall size, or you can even cut them all the way to the ground to essentially start again with a new plant. They probably won't produce many flowers the first year, but they will come back to full flowering the following year.
Here is advice for more routine, maintenance pruning:
https://www.gardeningknowhow.com/ornamental/flowers/camellia/pruning-camellias-how-to-prune-a-camellia-plant.htm