On your second question; If you are assigning a contract, let the asignee work out the details of where they want to close the deal. Unless you plan on getting paid your fee out of escrow, there is no need to even find a title and escrow company. You can do it with a one page assignment in most cases. For example you complete the assignment form, collect the cash and turn it over to the buyers. They will find a title company to colse the deal.
If however you are establishing an escrow account in order to facilitate the transaction, I personally like to use the same one over and over. Once you establish a relationship with a title and escrow company there are some nice things that you can get from them. For example if you just need a preliminary title report for a property you are looking at, generally a title company will charge you a fee for it if you are a one time customer. On the other hand if you have used them before and continue to bring them business, they will likely run those for you for free.