congrats on the bigger tank. remember to fully cycle the tank first before adding livestock. You can put the rocks in while cycling. You might want to give Iwarna a call to get them to deliver seawater for your tank since it is quite a hassle to mix that amount of salt water yourself. For me i started cycling with NSW as well and it really helps.
For your question, the three types of filtration on an aquarium system can be classified into 3 groups namely mechanical, biological and chemical. Most important to me is biological because it works the best. Place live rocks in your sump so the bacteria in the rocks can convert the waste into less harmful elements. FOr mechanical i think the use of filter socks will suffice. Chemical filtration includes the adding of Phosphate remove, carbon etc into the sump for best results.
NO need to spend on the led because T5 is cheaper. For the price, i do not think their led which cost $145 is any better than T5s. GO DE lighting website to check out their range. What you are planning to keep will impact your choice of lighting.
Hope it helps.