Can I substitute smoked bacon for pancetta for bolognese or leave it out

I'd do it, but trim the fattiest bits off the bacon first so there's more of the meaty part going into the sauce.

Totally different flavor. Adds too much oil to the sauce. Canadian bacon is a good option when available.

absolutely, yes. (Fwiw, I don't like pancetta and i always use bacon instead.)

It really comes down to whether you fancy the flavour of smoked bacon in your Bolognese. If so then do so, if not, then do not. Smoked bacon can add some depth to the dish, but if you are looking for a beef and tomato flavour to be the main aspect it can distract from that.