For the water protection the S5 by itself is already rated for IP67 water resistance, so unless you plan on submerging it and leaving it there it should be ok with getting wet occasionally and the Otter isn't much of an improvement on water protection for this phone. For the screen protection the tempered glass is probably overkill, I have a Zagg HD on mine and the phone is in a bumper type case with a slide-in belt holster. That does the trick for me. If you did go with an Otter the built-in screen protection would be sufficient, no need to add another one. Besides the possible fit issues inside the case, the double-layer of protectors might affect the touch-screen sensitivity.
As for the wireless charging it's not NFC that does that, you would have to replace the stock back cover with the one that allows wireless charging. Unfortunately that cover is a bit thicker than the standard one and would probably preclude the use of the Otter case, most cases will not fit with the wireless back installed. There may be some aftermarket options for wireless charging that fit inside the existing cover but I don't know how well those work especially with the added thickness of the Otter case between the wireless pickup and the charging base.
