I want to clarify, when you say radiator, do you indeed mean radiator? Or are you looking at the a/c condensor, which sits forward of the radiator?
That aside, OE radiator and thermostat, IMO. Had poor luck in the aftermarket with both. No RTV needed. Lube it with some coolant and toss together as per the appropriate torque specs.
For coolant, personally I use this stuff at a 60/40 ratio. Yes, this, specifically. Had a couple back and forths with the MFR about the formulation and a long chat about plasticizers, as well as it's ability to protect both iron and aluminum parts.
If you don't feel like re-inventing the wheel, use dexcool. PM me if you want to chat about it, else that discussion will derail this thread real quick. Meh.
Stick with spring clamps on the rad hoses. If yours are rusted, get new ones. I have a personal vendetta out against worm drive stuff (InB4 "they work for me").
Get a rad with a drain if you can. Much more sanitary when doing maintenance than having to bag off your a/c compressor and belt then rip the hose off and curse as it makes a mess.