The first answer is yes the final output resolution will be converted to whatever size and fps you select for the whole project
Now, I'm not new to this, I've been around for ages, but I often wondered why some of my video was not as smooth as I thought it should be.
I looked at the original raw clip - it played fine
I looked at the final clip and occasionally it was jerky in places
I had been filming in 25fps and outputting in 30fps
Once I learnt that about frame rates my videos are no longer jerky
So, you will have to keep that in mind if you are using a mixture of frame rates in your original. I would suggest you output at the frame rate that most of your clips have