I'd go for the Pro S out of the oils you suggested. It may be a fraction thicker when cold, but it's got a higher ester content than the Motuls (the Mobil has no ester), so more of it will stick to the metals of the engine and more oil will be in place for when the engine starts from cold.
A lot of oils are mineral based, but as a rule of thumb, anything under £40 (full price) for a large container (4 or 5 L) is very likely to be a mineral based oil. They vary in quality, some are good oils, others are very basic. If there are any you are unsure of, just ask.
Oil temp gauges are useful, especially in modified or tracked cars.
All additives claim to be special in one way or another, I wouldn't use it.