Do I necessarily need a high end computer to download modpacks through the technic launcher? I downloaded a modpack, which had over 100 mods, and it was not loading. I have 8 gb ram, and 1tb extra space. My graphics card is 600 or so.
It depends on the version of Minecraft and how many mods. For 1.10.2+ I recommend 2GB+ of RAM is allocated, since 1.12.2+ have gotten a lot bigger I'd say at least 3GB but 2GB still works at least for my PC which isn't anything special. With 600 it's not easy to tell but if it's a GT600 (I have a bit better than this and it's fine for me, my older PC could only kind of run 1.10.2) or GTX600 it should be fine but there is a big difference obviously.
I recommend a pack that has a good mix of things (depends on what your into when playing Minecraft), for me when I make a custom modpack I'm picking a few mods that interest me and set a few to serve a theme/goal or fit a variety of things. I make small 50 or less modpacks all the time and have just as much fun due to what I choose to put in and use/learn if it's a mod I'm not familiar with that I plan to focus on.
In my experience some Technic modpacks work, while others don't and I think it's more to do with the download link compared to the modpack. If it's saying it won't with the Technic launcher than that might be the case, if it's with the actual game loading up but not working and it can't load up a world/the mods aren't compatible for whatever reason, or Forge is outdated, then that's a different case. Could you give images if possible, it would help out a lot more.
You "might" be able to run the game with that many mods with those specs. i3 is fine, not sure about 620 UHD. I'd say try a few smaller packs and see what sort of memory/FPS you get.
Mind if you show the modpack mod list in a screenshot or just list them so I can work out the conflict/memory issue, it's not easy to tell with just specs and no information regarding the modpack/mods included.
Many times with mods it can be the amount of assets/the world gen is too much so that much memory can't be used to maintain it. Other times if the mod isn't finished, with the few I've tried the game is unplayable with mobs running everywhere and a lot of awkward things going on.
Many packs I know of that are big have about 4GB+ for recommended amount, 8GB is a lot but it depends on how much your system has and if it's even worth using that much. I know i have 8GB only but I'd never risk using 4GB as I don't need to and it really isn't worth it. That and if I don't use all the mods why would I bother wasting memory on it to have fun, you don't really need to.
You don't usually need a high end PC to run Minecraft with lots of mods even for 1.12.2 but if you do it's not worth it, mine was like $800 for a average one and I run Minecraft fine compared to a old PC that was more 90's/00's suitable and running even 1.10.2 with less than 20 mods and it was not that playable. For me I run about 50 or less (depending on the mods) and it works fine, but I have very different specs to you in terms of processor and graphics, but I'd say mine are slightly higher but I don't know for sure by how much.
From what I could find the specs you have fit a good enough PC/Laptop/Notebook that is more suited to typical tasks which even an i3 is aimed for so it could work but it's not really recommended to run Minecraft with that many mods on that, less than 30 at least (depends on the mods/assets/what they do).
Second, I see a problem with memory. Modded MC 1.12.2 was a memory hog. It might require more than 4G allocated, which is not possible with your current specs. Never allocate more than half your system RAM to MC.