Or the buyer could just miss a notice that the loan has been transferred to a new loan servicing company (as they do, loan servicing companies are terrible IME), and miss some payments by accident, again negatively affecting your credit.

These services are transferring live owners who have agreed to a certain % of the zestimate. 

If so, you must report the sale on Form 8949 even if you have no taxablegain to report". 8949 reflects the depreciation which transfers to Schedule D.In this situation, I do not believe there is a need for Form 4797.

Then if you want LLC as asset protection, you have to transfer the property to the LLC to hold the title.

We are considering transferring the title of our new rental into an LLC partnership.

Is it recommended to have a separate checking account for this or we can get it transferred to our personal checking account?  

I've been mostly torn on this issue, which is why I haven't transferred it out of my name yet.

What are the differences in transferring with a Quitclaim vs a warranty deed? 

Next, create a quit claim deed to transfer your property to the LLC.  

It makes transfers(if required) much easier.