75 Gallon makeover

I previously had a 75 gallon fish tank running with only a Marineland Emperor 400 w/ a bio wheel. I am now running a 10 gallon refugium along with that with a "hoopdy" return and a filter sock over the intake. The refugium as of now only contains live rock and sand. I am currently changing over some rubble/sand in a 5 gallon bucket with a 30watt light over it. I plan on adding that into the refugium and also chaeto. I have also thought about mangroves but am not really sure if there is room. Possibly if I only do a protein skimmer I can add another refugium in the sump. I plan on raising the 10 gallon refugium then building an overflow into a 10 gallon sump. I already have a tank for the sump though. I just need to design an overflow. Now my question is if I should get a cannister filter or bio balls. I have partially researched into both of them but still do not fully understand them. I also am curious of if a UV light would be good since I have a before major but now minor algae problem. Also I do not fully understand protein skimmers. I want to add one but have heard they are not necessary unless if you have a reef but there is always a possibility of me wanting to convert.

To just give a brief history on myself, in my previous years as an aquarist I was just a little kid that wanted cool fish. I successfully have had a freshwater 46 gallon bowfront with two oscars. Until I decided to have it as saltwater. Unknowingly I built a reef with very much ignorance. I only had a little power filter. I added all the right supplements tot he tank for the coral. For a very long time the soft corals continued to grow larger and larger even under low lighting. I then moved onto a 75 gallon fish tank along with the 46 gallon. The 75 had a 10 gallon refugium with live rock and chaeto. I wanted cool fish so I had a cortez stingray. I know this was very wrong and almost torture to the fish. I successfully kept and fed the stingray for 8 months. It then died after getting an infection from a cut from the heater. My mistake was not putting the heater in the refugium. I then got my yellow tang and blue tang which are now about 1.5 years old. I also had a 10 gallon tank with 2 seahorses. I did not let this tank properly cycle so both of the seahorses died during a nirtrite spike. I then lost interest in the hobby and would only feed my fish once a day and clean the tank once the month. Now that I am older i feel as though I can better understand all of the technology and chemistry.

I have big plans for this tank . Here are some photos of everything as of today November 30th.

My plans that I want to get done asap are to:

Purchase a clean up crew
Nassarius Vibex- 30
Nerite Snails- 5
Fighting Conch- 1
Red leg hermits- 15

Purchase Chaeto for my refugium.

Begin working on my sump.
I need help deciding what to put in it. I am open to any ideas.

Please state opinions and help me out, I want this tank to be worth all of the money