Car seat help

Okay, so I just came across a tik tok and saw someone make a cute video with their toddler in the car seat but sooo many people said the car seat was wrong. So I’m wondering if mine is wrong!! I always thought the more attachments you have the better. But if my son is 3.5, forward facing, he’s in a high back booster with harness. I have the latches in the seat, the seatbelt thru the back, and the back latch behind the seat. Is this not correct? I saw that latches are not to be used forward facing? So just the seatbelt in the back, back latch with the harness? I feel like it’s so lose on the bottom with just that. I tried that originally & the bottom came up so much. Thank u!!