Hi. From your post, it seems like population might be one of your priorities but not the variety of buildings? I am not really sure what else you want from the game so I can't quite excise all extraneous information so YMMV applies.
1. Epic buildings can be built at level 24 onwards. Each completed Epic building supports a higher population than any other residential building excepting the new OMEGA buildings. A completed Epic building gives a bronze/turtle, silver/llama or gold/cheetah token PART daily depending on the quality level you reached when you upgraded to Epic. Multiple token parts are used to make a token which in turn can be used to speed up production for an hour on stores... speed increases are 2x for turtle, 4x for llama and 12x for cheetah. If you plan on winning or placing in the 2 highest leagues in Contest of Mayors, you probably need these tokens. CoM also has assignments of earning Epic points gained while upgrading a building to Epic.
2. The last time I looked this up, the city on FB can't be deleted or changed except by the initial city you linked. If you need to back up your new city, you might consider using Google Play (which I have found unpredictable for adding neighbours) or another FB account.
3. Global HQ has been affected by the behaviour of Mayors during CoM. More items are being made and traded and many of the things that might have been hoarded get sold to make space to store items for CoM tasks.
As for a search function, EA have given their reason for why it is not easy - it is in the Announcements section of this forum. I can understand it given the volume of transactions but most people don't seem convinced. Have fun!
