I used #10 wood screws for mine.
It should carry the loads without any problem. Would recommend a deck-type screw or wood screw; not a drywall screw.
I used Simpson 10d 1-1/2" hot-dip galvanized deck nails without any problems
If they are stainless steel you can not paint them. If they are galvanized, you need to wipe off the coating with a good strong cleaner to remove the coating. After that put a good brand of spray primer (I used Rust-Oleum) and paint the color of your choice. You need to have a good adhesion of the primer so the paint does not peel off. Simpson also has brackets that are pre-painted but those are more likely a special order. Good Luck
Use the Simpson Tie fasteners that are required. You will have no problems then.
They are galvanized, so they will last outdoors. To get an even longer "years to maintenance" you might consider coating them with an outdoor primer/paint.
Joe, just go to the Home Depot website and enter that product name (or the SKU if you know it) and select a quantity of 12: https://www.homedepot.com/p/Simpson-Strong-Tie-3-1-4-in-18-Gauge-Gusset-Angle-GA2/100375243 Hope this answers your question. Rich Kahn