On Question 1, yes they lose some energy and the plant itself cannot concentrate just on new canes. It has to feed the old canes too. So maybe you would have a bigger crop if no floricanes. How much bigger though is the question?

On 2, not sure? I think you need to experiment. They say it should give you a big fall crop. But I think it depends on cultivar. My Fall Gold gives a decent fall crop if no floricanes, or if floricanes. So it makes sense for me to harvest both with that cultivar. I'm confused by the advice myself as I don't understand how 1/3 of the plants (fall crop) will produce more than the other 2/3 (summer crop).
My summer crops are huge!

If you want fall raspberries you need to prune all of the canes down in the winter.

Scott

I have Caroline in Nor Cal. Gives me fruit twice, cut the top 1/3 off the priomcane after it fruits. Cut the floricane the next year after it fruits. I'm sure the fall crop would be larger with no floricanes but I prefer longer season of raspberries.