-Archon is a title, and appears in the text box. Archons can use, or be targets of, any card or effect that requires a "titled vampire". The title does not give a vampire any votes.
-Only Camarilla vampires can be Archons. If an Archon changes sect, the title is lost.
-A vampire can only have one title. If an archon gains a new title, all archon abilities are lost.
-If you control a ready Prince, your Archon(s) may enter combat with any vampire controlled by another methuselah as a D action.
-If you control a ready Justicar or Inner Circle Member, your Archon(s) may enter combat with any vampire controlled by another methuselah as a D action, and Blood Hunts cannot be called on them.
-The Political Action card "Archon" is uneffected, and will still do what it always did.
The advantages of having the title inherent to the vampire as opposed to using the PA "Archon" are many: The title cannot be revoked by a referendum. It does not require taking an action to get it. You don't risk losing the referendum. You have to have a Prince or Justicar to attempt the PA "Archon" anyway. If you don't have a Prince or Justicar controlled, you can still bring an Archon into play (though the title won't be worth anything.)
The disadvantages are that if all of your Princes or Justicars are ever in torpor/burned, your archon loses his abilities - at least until you can find a replacement Prince or Justicar. But if you're in that predicament, having an impotent archon is probably fairly low on your list of immediate concerns. Also, the D action to enter combat is not at +1 stealth.
Note: The same set of rules could apply to Templar for the Sabbat. I haven't had the need to create any of those...yet.
Note II, Return of Note: I consider Archon worth +.5 capacity in my card creation formula.