Finally! NM is working as intended at boot. I didn't recall KDE wallet popping up asking to be configured. I got the wallet wizard after logging into the DE. I disabled KDE wallet via KWalletManager following instructions
here, rebooted and wireless interface is up.
Thank you all for your input. Especially kikinovak for pointing out that I cannot use both rc.inet1.conf and NM. And Andrzej for confirming the NM can do what I wanted and just "works".