You should switch all three to towns and grow them as quickly as possible as I explained here:
https://forums.totalwar.org/vb/showthread.php?t=114830
You need two citadels; one specialized for the knight’s guild and one for the archer’s guild. I chose Nottingham and London, respectively, because I got them up to the 9000 population threshold first. This allows you to get a big technological advantage. Send your merchants to Timbuktu and Arguin and you will never miss the income these two might make as cities.