i have the lincoln weldpac 100, 110v set up for fluxcore wire. it did fine welding in my mustII crossmember and boxing the frame. you have to grind fluxcore welds to make them look right. my welder is 20% duty cycle. i bought the 110v unit for portibility.
i won't say a welder is a welder, but a lincoln weld is a lincoln welder. input voltage has nothing to do with output voltage. if you look at lincoln's 2 small mig welders the 140 & 180. the 140 is 110v in, 30 to 140 amps & 33v out. the 180 is 220v in and 30 to 180 amps & 34v out. you can weld the same stuff with either one. the higher the amperage the thicker the material that you can weld in a single pass. you can weld thick materials with a small welder by doing it in mulitple passes. more heat on most materials will warp & stress the metal. usualy multiple passes is preffered over a high heat single pass.
the 110v lincoln will weld anything you want to weld on a car or truck. yes it will weld a frame and do a fine job at it. you must live within the duty cycle of the welder. the duty cycle is rated for maximum heat, at lower heat (that you will use most of the time) the duty cycle increases.
keep your 110v unit, it will be fine. i keep mine setup for fluxcore and do not own a bottle, but i wish i had a gas setup for mig.
i do have access to a mig at my friends shop, we do production ss exhaust welding with a 180t, often welding an hr with it.