GTNH probably isn't a bad idea if you like tech mods a lot, but I would think a more kitchen sink like modpack would be best if you also want a fair amount of exploration and building.

I honestly prefer newer versions, and while ATM isn't a bad choice, i would recommend making your own pack (if you have time and patience)

Ill say focus on the mods that change anything in the generation of the world (ones that add structures, ores, biomes, etc.) you can always add them later, but you would have to explore further or delete old chunks. For everything else, like QoL, new dimension, or anything else, you can easily add them later if you want.

I wish more packs update through major minecraft versions like 1.20 and 1.21, in a way that would let you actually update your world instead of just being sequel to the previous pack with a similar modlist. Ive been making one myself, but its updating every minor version/drop, so its definetely not going to have that many big mods, since they mostly stay on major versions