just a heads up, if your gonna be running multiple 45 gallon buckets your not gonna get away with just a 70-100 gallon res. To get your desired nute level you would probably have over 30 gallons per bucket.
My 14 site setup uses the 27 gallon bins and I only have about 13-15 gallons per bucket. My 100 gallon res almost overflows when I shut the pumps off. When I turn the pumps on it brings the water level down to about 40 gallons in my rez until the water returns back down the 4"drain pipe. I also have 1-1/4" check valve on each feed line... without those I would have about 210 gallons on the floor.
Any reason you would want to run these style buckets over say homedepot buckets or those nice looking buckets socalsiner is running.
whatever you decide on doing I wish you luck. I just got everything dialed in the other day in my system and its the most amazing thing I have ever seen... well worth the time, $$$$ and studying to create the system haha