It def cuts the process down. You will still go through the ugly phases but I was fish in in about 1 week. I watched closely and went slow on fish to build the bacteria without overloading the system
Short answer is yes depending on lots of variables. Roller mats from my understanding replace using filter socks so depending on fish load, feedings and other variables you could possibly get away without a protein skimmer
You can find lots out there. A simple 40 gallon breeder tank will work with a few simple mods. I’m sure you can find lots of sump not being used here as well
is your tank already drilled or you going to use a hang on the back style overflow?
Agreed on too many fish and likely getting aggression issue. I looked closer at those pics. I think those are flukes on the tail fin. Need to freshwater dip