There have been a lot of threads about this, so clearly few are even bothering to search the forum for existing threads and the wealth of information in them.
Sprint is a CDMA system like Verizon & USC. CDMA per se is incompatible with GSM, which is what most of the world uses. The Sprint S5 only supports some of the most common GSM frequency bands and moreover will have a locked bootloader and SIM.
Sprint will not unlock the SIM (actually SPC code) to allow using it with other domestic carriers. You can find third party vendors that will "SPC unlock" your Sprint phone. But then you will find that Sprint's S5 won't support any of the LTE bands on other CDMA or GSM carriers and misses some GSM bands too.
Nor can you use custom ROMs, kernels or recoveries in the normal manner due to the locked bootloader. You could probably use the Verizon Safestrap method to emulate a limited palette of custom ROMs, but you would have to do your due dilligence there and look into the details.
In short, if you jump through enough hoops, you can use a Sprint S5 on another carrier like TMobile. But it will always be marginal. You won't get LTE data speeds, you will see more congestion than those using native handsets, due to your reduced number of bands. And you may have no coverage at all in some fringe areas served by a TMB band that your handset doesn't have.