I have two old Realistic TRC-217 hand-held CBs and they have a High/Low transmit switch. According to the site below the output power is 2 Watts on Low and 5 Watts on High:
TRC-217 40-Channel (210-1644) Specifications Faxback Doc. # 16619
Power Output:...Hi = 5 Watts
......................Low = 2 Watts
Specifications are typical; individual units might vary. Specifications
are subject to change without notice.
In testing on level, open ground with no obstructions I found the range to be around 4-5 miles on High with the antenna fully extended. Fully extended means about 4 feet of antenna held up over my head. Kinda hard to use that in a Jeep while you're bouncing around off-road, plus all those hills and washes mean you need a really good antenna, which these do not have. The newer ones with the "rubber ducky" style antenna would be even less effective.