Yeah, league has separate mmr for ranked and normals, so you always get sbmm no matter what. Main difference is that in ranked, you're locked in regards to who you can queue with so there isn't too wide a gap in mmr, whereas norms let's anyone queue together.
League also doesn't do ranks directly based on mmr, but rather indirectly through an elo system, where your mmr decides who you play against do it's always a close to even team, and then the mmr decides how much a win/loss effects your elo. If you're a high rank player skill wise, your mmr will put you against similarly skilled players, even if you're still a lower rank, and it will just give you more upwards ranking.
That's what league does. If it detects early on that you're probably a smurf, you get tossed into smurf queue where you'll face other experienced players, and it's pretty reliable. Both times I've made new accounts, I've almost immediately gotten placed with experienced players, usually before the account graduates beyond bot games