Well, it depends on the pack, but 10 minute load times and rolling lag spikes from the insane memory bloat of 150 mods I'll never touch do tend to put a crimp on things. I've seen some really egregious packs where progression in a tech mod is gated by having to mess around with flowers and "mana steel" or concentrated pixie farts or whatever. The Enigmatica packs for example perform abysmally on my system compared to lighter packs, even after I wasted a couple of hours trying to optimise settings and troubleshooting all the cruft they shovel on.
I have been enjoying Engineer's Life 2 in single player, it's quite well put together and the changes it makes have good thematic sense - main complaint is that it doesn't include Create. I'm now starting to explore Fabric packs but from the looks of it they still have years of catching up to do.