I've recently dipped my head into the resource pack box, looking for "hyper realistic" resource packs to pair with my shaders (I'm mainly doing this on 1.12.2) I've found a great one, and at the moment I'm using a 1024 pack, but the problem is, when I try to run a 1024 pack (Laacis2's Natural 1024) it can take up to 10 MINUTES just to load into the game at all, which is confusing, due to my high spec, custom built PC. I tried using a 2048 pack, but the game refused to run at all and completely crashed my PC for around half an hour due to the amount of strain. I'm not sure on what is wrong with this, any information and or help would be greatly appreciated.
All that power in your graphics card is going to waste if you don't have Optifine installed. The default minecraft renderer is **** and always has been. Optifine will give you a big boost in performance. Understand, however, that Minecraft is not the latest Rainbow 6 or Call of Duty. The environments are autogenerated and player modified... not carefully designed to limit the number of textures and polygons on the screen at once like your normal AAA title would be. Additionally it's written in Java... which adds a lot of overhead due to the JavaVM and wasn't really designed for games besides.
Where super-high resolution textures might not make your system chug in Skyrim... it still can in Minecraft simply because Minecraft asks your computer to show so many of them at once with no regard for how hard that would be to render. Also consider also lowering the number of chunks rendered in your options. And get Optifine... chances are you aren't even getting the full benefit of those resourcepacks without Optifine... a lot of (the better) resourcepacks use features optifine adds. Lastly, if the game simply outright crashes when loading with especially large texture packs, chances are the java vm isn't able to allocate enough ram to the game. Since you have 16gigs of physical ram consider changing your -xmx setting to "8g".