I’m not understanding your question? Chosing TBs and Collecting City Coins/Prizes are unrelated Topics?
I Collect City Coins/Prizes 22-24Hrs and Mostly Brown Boxes for my TBs.
When you first start on CW, NGs TB info works! But as your City Grows to a HIGH Gem Value, your Brown TB Box will “Max Out” (about 1.8M Gems) and give you the same Prizes as the Longer Timed TBs.
Also your HMP Building Reward has a LOT to do with the Size of your TB Prizes even if your City is not “Maxed Out”!
That is why it is Very Important to have a Constant Building Program to KEEP your Building HMP as High as possible in your beginning.
One thing you can NEVER Predict is under which Box the HIGH TB Multiplier is? Like @NashRivers said above, That 2Hr TB had a SUPER High Multiplier and the 4Hr TB did not. But at least those Bubble Boxes worked, LOL!
I use the CW App on my Phone and Also the “Hey Google” Feature, LOL! “Hey Google, set a timer for 10mins”! I can open a TB anywhere/anytime. I opened 1310 TBs last month! I LOVE CW!
And like @papa_meester said, It took me about 2Secs to Swap that Purple Box Challenge, LOL! I Super Rarely use them.