Should this 3/8 impact be enough for DIY projects, rotating tires etc? Or should I get the 1/2 in instead?

95% of all car/truck lug nits will never come off with this 3/8” Impact Wrench, 15% will not even come off with the 1/2” Impact wrench which has 4 times the power at 650 foot ponds of toque

It's fine for rotating tires. At 150 ft lbs it should be able to handle any lug nuts you face (most cars are 75-90 ft lbs). For basic around the house tasks it will be fine.