So, I've been able to get 106/109, but there are no more to find that I can see- my sense is that there are 3 pairs of cars to get so you need to be like over 5, which is almost impossible in 10 minutes. Are there small things that are hidden that I'm missing? Please help.

I only collected 108 twins but got 100%.

There are no cars to collect. TThe ones I had a hard time finding include: mermaid/mermen out in the water, the skate guys to the right of the school, and manhole covers. I plan on posting a list of all the twins when I get it more accurate.