Jamiel, 1st gens did not come with fluid recovery bottles so I don't have one. I fill the radiator at the cap. I periodically check it to see it it's close to full. If I drained it all for a coolant change; I fill it, start the car and let it warm up until the thermostat opens and you can see coolant flowing. The fluid level then drops as the system fills. I keep adding coolant until it's near full.

In all my years and miles I don't recall having pressure pop the 15# cap and have fluid dump out the overflow.

I've never thought about expansion but would think the heater and radiator hoses offer some expansion as well as some trapped air and as mentioned earlier, when cool it's full down 3".