The GTX 1050 Ti model is capable of reasonable frames when used with LSPDFR, provided you're using reasonable settings for GTA V itself. Be warned that using a lot of plugins (especially resource intensive ones such as LSPDFR+, Traffic Policer, Safer Chases) will cause frames to drop further. As long as your expectations are reasonable and you don't plan on maintaining 60 FPS all the time, this is a good budget buy if you aren't willing to/able to spend more.
256GB is enough for basic computer usage and installing GTA V, although you will want the hard drive for additional storage. GTA V itself will take up a good amount of the SSD on its own.