Does Time Capsule switch between 2.4 and 5 ghz seamless on the same SSID?

If I leave it setup as is will it choose 2.4 or 5 ghz broadcast by it self without the need for the 5ghz network to be name different?

Yes

If your Mac is close to the Time Capsule, it will connect at 5 GHz automatically. If you move the Mac three or four rooms away....it will likely connect to the 2.4 GHz band automatically.

That's because the 2.4 GHz signals are stronger than 5 GHz signals, so 2.4 GHz signals travel further and penetrate obstruction more effectively than 5 GHz signals.

Botttom line...your Mac will "look" at both bands and automatically connect to the best quality signal depending on where it is located in relation to the Time Capsule.

Some other info you might find helpful:

I'm in an apartment complex where those who still have land lines (remember ye old days: 56K modems and Osbourn and Altair computers with 8080/Z80 processors when 64K was max memory...but I digress) [they] are using wireless phones and you probably guessed it: many of them use 2.4 Ghz and eat up the channels while they're at it! (along with plenty of interference to your wireless setup). Trust me on this.

Therefore I would recommend for your consideration that you stay in 5 Ghz land even if it means giving your bank account a heart attack for shelling out for booster amps and a bunny ear (rabbit ear) for xtra range.

Also hold the option key down (keep holding it) when you click on the wireless icon next to the sound icon of at the top bar on your screen; and you'll find the signal strength where less is more: i.e. a lower number is what you want (so a lower negative number really is more!)

cheers...