Just to add-on to what Clanger said, we all talked about this in another recent thread, someone was asking about things like ReviOS, SpectreOS, etc. All those "gaming" editions floating around on the internet... The problem with all of them is there is no transparency (or it's quite lacking) and you just have no idea what is or isn't in them (perfect example here, OP stated this Windows ISO is full of crap like startisback, etc).
I'm not just talking about security issues, like someone sticking a virus in there, but rather a lot/most/all of these guys don't do that great of a job testing these things. You can see it for yourself because they use tons of registry keys that aren't even valid for those versions of Windows. There's so much misguided and incorrect information out there on tweaking, and since all these website articles just copy/paste the same stuff from site to site we end up with all this "gospel" information which is actually wrong, and then these guys use that information to build gaming images. At best those tweaks do nothing and it's just taking up registry space, and at worst they slow things down.
For example, SpectreOS compresses all files to save some disk space... This doesn't make sense in a "gaming" ISO because compression requires more resource overhead (CPU/Disk activity) to uncompress and load, which then contributes to slower loading times in games. Also, if you play a game that streams graphics textures, which quite a few of them do, then you can potentialy see artificial hitching and microstutter that wouldn't otherwise exist if you weren't compressing everything needlessly.
TLDR: It's actually faster to use a clean Microsoft ISO and build your own tweaked edition than it is to try and reverse engineer these other ones.