For all modern aircraft, particularly with jet engine aircraft, both the upper deck where the passengers sit, and the lower deck cargo/baggage compartments are pressurized. Since outside pressure at cruising altitude (30,000 feet) is about 26kPa, the cabin and cargo hold pressure is lowered to about 76kPa so that the aircraft fuselage will not burst due to the high pressure differential. With some earlier jets, the AFT cargo hold may not be pressurized which means that the AFT cargo hold pressure can be as low as 26kPa at cruising altitude. Some of the very old reciprocal engine aircraft flying in South America, Africa and the former Soviet Union countries are equipped with non-pressurized cargo holds. Therefore, you need to watch pressure differentials when your cargo heads to such destinations.
Human skin is used to the standard atmospheric pressure of 101.3Pa, and our pores are made fit for such pressure. Air circulated inside the passenger cabin is drawn from the engines. It is very dry. Humidity is added yet the air is still very dry. Water gets out from the opened pores. Passengers need to drink lot of water due to the low air pressure inside the cabin as compared to sea level coupled with its dryness.
Passengers experience the same gravity force that cargo feels. This is no different with any type of aircraft, large or small, or reciprocal or jet engine. Passengers brace themselves with seat belts at take-off, at landing, and when encountering turbulence. The same G power is on the passenger. Cargo must be tied down as they do not use seat belts. ULDs must be secured to the aircraft restraining system.