Without a tripod you will have to have a very steady hand to make real use of the length of your 70-200mm, so I would go with the 24-70mm. The wider end will allow you to take in the majority of buildings and the tele end will let you zoom in on features.
There is little point in using Shutter Priority when photographing static subjects. You will be much better served by Aperture Priority. Open the aperture up when photographing, say, statues, to blur the background, and use a general aperture like f8-f11 for architecture.
Your ISO will depend on the light. If it is a sunny day, 200 is fine. 400 will give you more shutter speed leeway on an overcast day. You will very probably have to crank it right up to shoot inside a church without a tripod. You may have to improvise by resting your camera somewhere to take longer exposures.
Generally speaking, centre-weighted metering is the best overall setting (in my opinion) for most situations. However, if you are shooting statues against the sky you may want to switch to spot-metering to avoid silhouetting.
Of course, all this is general: you can always change settings on the fly as and when you need to. If in doubt, try popping your camera into P mode, where the camera will make most of the decisions for you, but still leaves you control over most of the settings.
