But keep in mind that, if the sensor size is the same, Camera A can actually give you a lower quality image, since the size of each pixel is smaller (more pixels being packed in the same sensor). This is particularly true in terms of low-light sensitivity (ISO), since each pixel will have to "work harder".

Once the preset it's saved, when you are importing new photos, on the right side, in the "Apply During Import" menu, select the preset you just created under Develop Settings and the lens correction will be applied to all images you import, selecting the correct profile to every lens you used.

No need to go to the Manual tab; when you select "enable profile correction" (under the basic tab) it will automatically select and apply the right profile (you can go to the Profile tab and confirm it selected the right combination of camera + lens). To add a Preset, first apply the changes you want to save as a preset (in this case, only the profile correction) and then, on the Presets Panel (left side) click the + sign next to the word Preset and, on the popup screen, select only the Lens Correction option and save it (check it our here i.imgur.com/Wzu6Sh7.png)

Not if you leave the lights off until the end - remember, we are talking about an exposure of many seconds - to a few minutes.