For the ACES suit that you show in the question, there is an integral pressure controller that determines what level the suit is pressurized to.
...pressurization begins when the cabin pressure altitude rises to
around 35,000 feet and is “hard pressed” (3.67 psia) above 60,000
Note that your assumption that when the cabin altitude is sea level, there is no pressurization, is correct.
Source: SCOM, page 2.10-4
Rough equivalent pressure for the cabin altitudes given are 3.5 psi (35,000 ft) and 1 psi (60,000 ft).
Source: Air pressure at altitude calculator
The maximum delta pressure between the suit and ambient pressure is controlled by a positive pressure relief valve (PPRV) that is part of the suit controller. This valve cracks at 5.5 psid and closes at 3.5 psid. This valve keeps the suit from becoming too rigid if, for example, the suit is closed up with a 14.7 environment inside and the cabin pressure subsequently falls. The PPRV vents gas to maintain the proper delta pressure and prevent the suit from swelling up.
I don't have a great reference for this (personal notes) but it's at least referred to in this paper, page 20.