a lot of your questions are dependent on who the beneficiaries of the estate are, the size of the estate, etc.
Best to find a estate attorney and a one hour discussion should give you the best guidance on the approach ; could save you a lot of headache if he/ she says a separate return is not necessary. it'll be worth the cost of the 1 hour.
As to the question of 'which product', if the estate is required to fill out a return, it's the Form 1041 that you are looking for in the product and then each beneficiary would receive a K-1. since this may only be a 1 year effort, might be worth a tax accountant as that Form 1041 is very different from the Form 1040.
Also, income reported on the Form 1041 is at a very high ta rate - max tax bracket of 37% at just $12,500 of income, so best if it's distributed to the beneficiaries via the K-1 as they will pay income at their tax bracket (AND YOU CAN DISTRIBUTE 2018 INCOME AS LATE AS MARCH 5th), so best to figure this out quickly
