My DH & I are the same as you.
Only we both occasionally smack. Only when its something dangerous at her age though. As they get older its more when we just get pushed too far, but we are really trying to steer clear of smacking all together atm. Its not easy. DH thinks its the way to go, I don't.

DD2 knows whats right & wrong most of the time now & will look at me while doing it & wait for my reaction with a grin on her face. She's just testing her boundaries, but they do still get very frustrating.

When my girls were about that age I used to explain why I didn't want them to do something & distract them eith something else.
DD1 was pretty easy. When they get to the picking up naughty words age DD1 started it, like they all do. I used to say 'thats a naughty word & it's not nice to say'. She stopped after a few tries & used to tell us off if we said a naughty word.
We are still working on DD2. She's not out there with it, but occasionally she'll say one. We were about to get in the car the other day & I told her to go to the toilet first. She looked at me in all seriousness & said 'I not p*ss mysewf'. I had to walk away coz I couldn't not laugh.
She really only says them to stir DD1 up though.

So that worked for us. Everytime she does something, pull her up on it & say 'no that's ouchy' behind the TV or something. Power points in our house bite.
I taught DD1 about hot by getting her to touch the outside of my coffee cup. She was 8 months old & because she knew what hot meant & as she got older if I said something was hot she wouldn't go near it.
DD2 learnt to stay out of cupboards & drawers by getting her fingers in them. Not the best way to learn!

It could be harder or easier when you have the little one. DD1 was easier as she was besotted with DD2, but DD2 was ready for DS to go back the day after he came home.
She will settle down. It may take time, but it will get better.