You should read the horror stories about Red Sea tanks before settling for one. Personally that kept me away from these and I got a Planet Aquariums instead.
Pretty much any light will grow softies. Clams do require way more light, akin to SPS.
These days deep sand beds are not really common...
I must say I disagree with starting from dry rock. The "ugly phase" is really long (I have used some but just as a way to hold my live rock up: they looked terrible for a long time), and the pests that come from the ocean aren't that bad.
If you look online, even the people that were pushing...
For your live rock, make sure you get quality one.
Personally when I started my 55 gallon, I used the rock from my 25, then added cultured like rock from Florida I put my journey here and in the end, the best looking ones I got was from KP Aquatics.
But these days Marco Rocks also has some...
I used to love rimless tanks. But then I prefer my flasher wrasses in the tank and not on the ground so... since I will need a net cover, might as well get a regular tank. Mine is a Planet Aquarium. Built like a tank