Capacitor 1206 footprint: correct for the parts I will be using?

Yes you are, but that’s a good point to start from.

“Run of the mill” capacitors and resistors I use 0603 or if I’m tight for space 0402 . . . for low value resistors or high wattage you may well have to go bigger.

I can hand solder 0402 just about with plenty of light and a magnifier . . . JLCPCB should be able to do smaller than 0402

When you get to footprints that are not “run of the mill” then yes be cautious and check everything.