Can the TDAC card be filled out before the 3-day arrival date and do you still need to register with immigration upon arrival in Thailand?

What part of "Within 3 days " do people not understand. ?

No

𝘄𝗵𝗲𝗻 𝗳𝗶𝗹𝗹𝗶𝗻𝗴 𝘁𝗵𝗲 𝗧𝗗𝗔𝗖 𝗰𝗮𝗿𝗱 𝗼𝗻𝗹𝗶𝗻𝗲 𝗰𝗮𝗻 𝗶𝘁 𝗯𝗲 𝗱𝗼𝗻𝗲 𝗯𝗲𝗳𝗼𝗿𝗲 𝘁𝗵𝗲 𝟯𝗱𝗮𝘆 𝗮𝗿𝗿𝗶𝘃𝗮𝗹 𝗱𝗮𝘁𝗲

NO it can be done from 3 days before you arrive right down until you go to stamp in to thailand (there are kiosks in the arrival hall)

𝗱𝗼 𝘆𝗼𝘂 𝘀𝘁𝗶𝗹𝗹 𝗵𝗮𝘃𝗲 𝘁𝗼 𝗿𝗲𝗴𝗶𝘀𝘁𝗲𝗿 𝘄𝗶𝘁𝗵 𝗶𝗺𝗺𝗶𝗴𝗿𝗮𝘁𝗶𝗼𝗻 𝘄𝗵𝗲𝗻 𝘆𝗼𝘂 𝗮𝗿𝗿𝗶𝘃𝗲

YES just because you do a TDAC doesn't have anything to do with the TM30 you file when you come back in from abroad

Can only be done up to 72 hours before arrival. As for TM30 with immigration, that is office specific.