There are a whole range of cards, new and used, that will run off the power they get off the motherboard. The 750 Ti is one of those cards. The RX 550, 460, and 560 are AMD new cards that fall in this category, along with Nvidia's 1030, 1050 and 1050 Ti.
Considering your modest gaming needs, any of these cards will get the job done. There is a sizable jump in performance if you were to pick the 1050 or 1050 Ti, but does it matter to you? Probably not. So then I would just buy a 1030, not a 750 Ti. I doubt you'll find a new 750 Ti substantially lower in price than a 1030. Besides modest gaming performance, the 1030 gives you up to date outputs and video acceleration.