If I re-flash my current stock ROM with the same ROM, will it wipe my sd card data?

I need to reflash my ROM, but I don't want to lose my data on my internal SD partition. So what would happen if I flash the same ROM that I have currently?

I have the stock S6 ROM currently on my device (G920TUVU1AOCG_G920TTMB1AOCG_TMB)

I own 5 Micro USB cables and 2 Android phones and none of them all fit the same

I was forced to get a new phone (Nexus 6) after my OnePlus was stolen. The N6 I bought was used but in new condition and the guy didn't have to original cable. Of the 5 cables I own, 2 fit very snug and the others will literally fall out when you move the phone. I thought the phone had an issue so I was able to get Motorola to warranty it for me. Nope, new phone has the same exact I issues. One of the cables that doesn't for well is the stock OnePlus cable, the other 2 are good rated ones bought on Amazon. Is the normal? My other phone used for work is a Galaxy S4 and it too has issues with some cables.

Does someone make a cable that is snug and stays in for all devices?