Some users have recently had their accounts hijacked. It seems that the now defunct EVGA forums might have compromised your password there and seems many are using the same PW here. We would suggest you UPDATE YOUR PASSWORD and TURN ON 2FA for your account here to further secure it. None of the compromised accounts had 2FA turned on.
Once you have enabled 2FA, your account will be updated soon to show a badge, letting other members know that you use 2FA to protect your account. This should be beneficial for everyone that uses FSFT.
Yes, it will void your warranty. Especially if there's a sticker that says "Void warranty if broken". That sticker is usually one way to get into your PSU.
Buy some of my split loom (posted in the FS/FT area) and loom your PSU with that. It won't void your warranty since you don't need to open the power supply or remove any connectors.
Yeah, as long as you dont crack the PSU casing open you should be fine. I sleeved my PSU without doing so and it came out great!, just make sure if you need warranty work done, to remove the sleeving first