Snow seal will darken the leather.We used to use it on hiking boots
Neverwet is recommended for work boots,but not for fancier leathers,it leaves a haze.
One of the spray silicone designed for fabric or boots might work better
As stated Snow Seal will darken leather. I used it externally on the inboard side of an IWB 1911 holster as I was having trouble with the beginnings of very fine rust on the pistol from me sweating through . Rubbed it on a couple of times and warmed things up with a hair dryer. Haven't had a problem since.
Snow seal is great for leather. I put the can and the leather in the sun to soften it. The sno seal soaks in quickly and penetrates well.
I think you need to protect the gun with something else. I use XF-7, can't be beat for protection and lubrication.
I have no idea about the products you mention, but occasional removal of the firearm from the holster and an occasional wipe down of the surfaces of the firearm with a patch moistened with Breakfree CLP will protect your firearm from rust. Use traditional GUN CARE products on your GUN.
Your gun is neither a pair of boots nor patio furniture.
Be careful with what you use on your holsters, snow seal and the likes will break the leather down and make it soft and slippery if all you have is friction retention this is not a good thing.
I'll second Obenauf's Heavy Duty LP. I've been using it on my work boots for years, and the stuff does an amazing job waterproofing the leather yet allowing it to "breathe." Snow Seal, from what I've heard, blocks the pores of leather and makes boots really hot and unbearable to wear for extended periods.
I've also used Obenauf's on my Bianchi Pistol Pocket IWB holster, and I've never had any problems with sweat soaking through to my revolver. I even use it on my wooden stocks from time to time. It leaves a nice warm sheen and the oils really bring out the grain.
Give it a try. It's a little pricey, but it'll last you a very long time.