Regarding the six line wrasse, if he is the most aggressive fish you'll be putting in, then you have the correct idea of putting him in last. Haven't read of them picking at anemones (and if it has happened, it's rare). I hope you're not adding the anemone soon though.
You can have 2 clowns in the same tank, but they can be very aggressive towards each other trying to claim dominance (which will become female and male). Clowns don't always host anemones in captivity. Less of a chance if they are tank raised too. Breeding clownfish...don't know if they'll lay eggs and when the eggs hatch they will be gobbled up if not taken out right away. So, it's best to keep a pair in their own tank. Also, the fry eat rotifers which you'll have to grow unless you want to spend a ridiculous amount of $.
You can go with mostly base rock. I have 100% BRS dry pukani rock b/c it was more cost effective, and had no pests. You could also buy mostly base rock and then some LR
to seed it. The protein skimmer is going to be your largest investment. Getting a quality, reputable skimmer is important.