Upload & Sell: Off
I know I can come across as being quite terse, but that is not my intension
You can set up Photoshop so that you can switch the main view between full and soft proofing. After that you can toggle between the two with a key stroke: Ctrl+Y for soft proofing, and Ctrl+shift+Y for out of gamut colors.
View > Proof Setup > Custom…, then in Device to Simulate, choose the profile you intend to use, and the rendering intent, etc, then save it with a name that reflects the paper and the rendering.
After that, you can toggle between normal and soft proofing modes with the above mentioned shortcut key, at anytime you want when editing.
[The problem with converting to one color space profile from another, is that it is always done colorimetrically – ie. out of gamut colors are always clipped. It is far better to leave the image in ProPhotoRGB and then decide on the rendering intent at the printing stage. I know Photoshop implies that you can choose a rendering intent for a color space conversion, but it doesn’t work – color space version.2 profiles don’t have enough information to do a perceptual based conversion.]