I don't actually know if Forge mods work for Fabric on 1.7 (the legacy version), but for renewed I don't think it is possible. Legacy (and even renewed to some extent) is a big mod, so it isn't weird that it's lagging on lower-end computers. Have you tried using only this mod and not any other ones (except optifine)? The curseforge app isn't required to play the mod, although not using it requires you to install curseforge separately and add mods manually which can be annoying, so it can be very helpful. Sadly I don't think legacy is available on the app.

Well... I haven't tried it at all yet because I know that my device struggles with MC alone already so with this mod and the intended setup I can be absolute certain it wont just only lag but not run at all anymore. Since Minecraft (Vanilla) with rather lower to medium settings is already runing at bellow 50 fps. With Sodium I get more than 100 fps so I would try it this way rather than with anything else since Optifine doesn't help me at all.

But Sodium requires Fabric.

I already assumed it wouldn't work but I want to know for sure before I try much and end up failing.

Well shame... I mean... I haven't play minecraft for a veeeeeery long time and I remember how it was running on an acctual potato of a PC a decade ago and now it is overwhelming an admittedly low gaming device on low settings - but still... a waaaaay better device. Maybe I'll try it anyways just to be sure but I know... this just can't work out.

You could always try playing the mod with optifine and seeing if it works out anyway. Optifine might help with improving the mod even though it doesn't improve minecraft in itself.

My computer is relatively high quality but I have the same issue with horses and hobbits and many other creatures being entirely black and some things causing my entire screen to be covered by a single monochrome texture, I have tried multiple downloads, reinstalling forge, reinstalling all of minecraft and purging all of my files. I have nothing else installed alongside it.

That sounds incredibly strange, maybe you should try reporting it on the mod's discord server (if you dare) or maybe even to Mojang? You'll get much better support there than here, I'm not very clever on these things.

Not sure how this is similiar to a massive performance problem but well ^^

I have installed the mod now as it is told. With Forge. Just to check how it would work - I expected not at all but... somehow MC with this mod is running alot better than MC Vanilla. I have the suspicion that my incredible performance issues is caused by a later version of MC or maybe because the Mod does not have content you have in the vanilla game. It's really strange...

About your problem Dane-ish Gamer - have you checked out the tutorial of how to install the mod? I think there must been something wrong with ur installation.

Do you have the right version of minecraft / Forge?

Try to follow the tutorial step by step and make sure you have no texturepack or shader to make sure it is not caused by that. Sometimes I have graphics problems because of it.

But first install MC 1.17.1 and than start it and look if everything is right.

Than continue with the acctual mod installation. If it isn't working Im sorry... but that is my idea about this issue.