Software and hardware question?

[LightGunner89]

Hello

I'm going to attempt to hook up two pc's to an old CRT tv, preferably through RGB VGA. It's intended usage is mostly light gun games but some other types of retro games as well.

Currently I'm running one of the computers to the TV with a composite video rca cable, it's an old XP (32bit) machine with a Radeon HD 3450 graphics card with a mini DIN (S-Video?) out. Question one, is that mini DIN port always outputing 15khz or am I slowly destroying my TV.

With this hookup everything works as expected, but it is very hard to read stuff on the computer, sometimes impossible.
Like trying to do keybinds and calibrating my light gun, it hard to follow the instructions as I can't read them.

I have been contemplating on purchasing a sync converter for VGA to Scart, the Ultimate SCART adapter (from ArcadeForge) looks like the thing I need.
Do you guys think it would be suitable for for light gun gaming or will it produce too much latency?

On my other pc I have a GeForce GTX 770 graphics card, OS is Windows 7 64bit.

So the last question would be how to get my two graphics cards to output 15khz over VGA? I know of software like Soft-15khz, CRT_Emudriver and such but I understand that one might run into issues such as too high resolution/frequency at startup and some cards not being supported by the software.

Thankful for all responses!

Kind regards
LightGunner89