Can I claim myself to be and act as a safety pilot since I don’t have a SP rating on that aircraft
The OP is asking can he claim to be a safety pilot. The answer is no, he hasn't been assigned that role by his company. If he were the company would have protocols in place, such as responsibilities, who logs what, etc. You are just along for the ride, bringing the CoG forward a little, reducing available payload, but more importantly, gaining exposure, insight and experience as to how a SP operates versus a two pilot operation. We went from SP to two and it complicated things no end, turning it in to make work environment in order for both to feel they were there for a purpose. Would have been admirable if it was a IMC operation, but was actually VFR. There is always the redundancy argument of course.