Running a simulation

I used to be able to run a sim on the best in bags recommendation. Can you still do that or do I have to equip the gear, sim, and change gear and resim?

If you go to the simulator page:
https://www.askmrrobot.com/wow/simulator

You can load your character and simulate it. In the “Gear” section of step 3 in the setup, you’ll see a picker below your gear that says “Choose a cached optimizer setup” - you can use this to load in your BiB recommendations and simulate it.