Toddler Bed Switch

I was afraid that he will run away or start playing whenever I leave the room) I was surprised, but he never did it

those are my two main concerns lol either he starts playing with toys or walking out

I had the same fears. We baby proofed the room so he's safe if he gets out of bed. We also have a gate at the top of the stairs. So if he figures out how to open his door, he can't go downstairs by himself. He can only run around upstairs. He hasn't figured out doorknobs yet. But there are child locks you can get for bedroom doors that you could look into.
My son is pretty good about staying in bed at night but sometimes he'll play for a bit before he falls asleep and then get back in bed when he's more tired. He doesn't typically wake up in the middle of the night and get up and play.

My daughter slept in a toddler bed last night in her own room for the first time ever and she slept all night I nursed her to sleep first then just left her alone and she stayed. Mind you she is typically a co sleeper

I was realizing that switching his crib to a toddler bed, there’s not really anything preventing him from rolling off the bed unless we purchase the toddler rail. The mat is a great idea!

For me, I put him to sleep and once he’s all the out I close my son’s door and taught him to knock if he wakes up in the night. It’s worked 100% of the time so far and it’s been about six months. But I always make sure his path to the door is clear so his half asleep self doesn’t trip.