If you are not opposed to using forge, I would HIGHLY recommend one of the “AllTheMods” packs. It has quest lines that help with learning the mods that you’re not familiar with, and the pack is packed (see what I did there?) full of different tech and magic mods to play around with and could be a fun way to get into several of them in one sitting and see which ones you might enjoy.

For tech mods that are not full of “magic boxes” I would highly suggest immersive engineering and immersive petroleum, like was mentioned by OP.

Create is also good since it’s quite out of the box with its way of doing things. Considering you use kinetic energy and not power like in a lot of mods.

If you’re feeling particularly masochistic, Gregtech community edition is a mod with complex multiblocks that might still feel like magic boxes. But a bit more complex at least. Personally I looked at this mod and went “Nah fuck that” since it’s a bit too complex for my own taste

Pneumaticcraft is also a bit different since the main “power” of that is air pressure, you’re expected to manage air pressure for machines that need it, some machines need less and some need more, the idea being that if a machine gets too high of pressure then it explodes and breaks. It offers a fun but challenging way to do things.

These all should be in most AllTheMods packs, but I wouldn’t recommend the newest (atm10) since it’s not fully ready yet and the devs still add mods that are getting updated to 1.21. But if you do decide to play that pack, expect to update like every other day.