Baldur's Gate EET BiG World Mod install failure?

I realise that these forums in particular may not be the best place to post this, but I already have an account from a few years ago, so I figured it was worth a shot.

Recently, having EET come to my attention, thinking that it sounds like a blast to try out, and as good a reason as any to jump back into my favourite story. The only problem is.. I don't necessarily like using NMM-type mod managers, and BiG is no exception. Though, unfortunately, I was unable to find anything necessarily conclusive on how to manually install EET, as well as the few mods that I'd like installed (namely Tweaks Anthology, SCS, a general Bioware NPC banter mod, and a couple relationship mods for Viconia and Keldorn later on). So I settled to make an attempt at using BiG.

At first everything went fine, and I was rather satisfied with it's functionality, went through selecting my mods, made sure everything was compatible and such, the mods downloaded, began installing, and the BOOM, "Installation failed, you didn't make a backup file (or something along those lines), please make a clean installation of BG2:EE and start again."

This has happened twice, I've tried making several "backup files" on several different drives, and I repeatedly get the same failure message.
Any tips/pointers?

Thanks~