Is a 20 amp 2 pole Tandem, the same as a 20 amp 2 pole ?
I do not know which breaker to use - i.e. one about 1 inch wide or
The one that is about twice that size. Also, what gauge wire and
Breaker size do I need for the following:

I bought an Wall Oven and Drop In Cooktop
The data plate on the Wall Oven shows:
208Y/120V Kw 2.7
120/240V Kw 3.6

The data plate on the Drop In Cooktop shows:
/208V 5.00 Kw
/240V 6.70 Kw

No, a tandem is two separate switches in one housing designed to plug onto only one hot bus of a panel. Note that is will only be rated 120 volts. A true 2 pole breaker will be rated 120/240 and have a common trip internally between poles, and designed to plug onto both hot bus of a panel.

Watch out, some manufacturers make "half size" two pole breakers, they look like tandems. Read the data on the box or label on the breaker. These are fine for space saving in a panel when needed. Confusion is they look like tandem breaker which may get used instead of a true 240 volt 2 pole breaker.

A standard 2 pole breaker will be full size, usually 2 inch wide, and a handle across both poles.



Assuming you have a single family home with typical 120/240 volt service:

While both units total 10300 watts, you are allowed to connect both of these to one feeder to be considered as one standard range, and rate the circuit at a demand rate of 8000 watts, and run the minimum size feeder of 40 amp.

This will require a minimum of #8-3 plus ground NM-B Romex cable.

At the oven or cooktop, stop the 8-3 in a junction box and connect the two whips, one from each appliance, use all the proper cable connectors, and splice in a 4-11/16 inch square junction box, using large blue wirenuts, and cover the box with the proper junction box cover.