Bank of America tends to be conservative in their estimates. The builder's mortgage company, MTH, will likely do everything in its power to close on time. The other lenders may or may not actually close at the time and under the terms show in their GFEs.
Remember that an estimate is still just that, an estimate. Some borrowers expect that the cash to close will not vary from what they were told, but the reality is that it can. A last minute surprise of a few thousand dollars can really wreck your plans. A few lenders guarantee their estimate. Some may tell you they can close in 10 days and then 8 days later say it will be next week. Don't be surprised.
Closing costs will vary based, first on the exact date of closing, because daily interest is charged until the end of the month of closing. A lot of lenders use the 15th and don't adjust their prepaid interest number to match the actual anticipated closing. Other lenders will estimate insurance lower than you might be able to locate. So, remove prepaid interest and insurance and compare all three again. Taxes and other costs should not vary on what is left. If MTH is still lower, then it is likely the best deal, provided there are no discrepancies in the documents delivered to the title company. Yes, occasionally some lenders quote one rate and then the documents show a different rate on the note.
If you see different charges among them, like one charges an administration fee, and one charges a high tax certificate fee and so on, those are what you are comparing. You will get your own insurance and it would be the same number in all 3 scenarios. The daily interest, similarly, would be roughly the same for all of them on the same date of closing.
But, having disposed of variances in timing and actual costs, if the MTH GFE looks the best in terms of cash to close and monthly payments, then it probably is. (Remember to back the daily interest unless it is calculated for the same closing date by all 3, and to back out the insurance unless it is the same estimate for all 3.)
Shop around for insurance to get a decent provider. I can suggest one we often find is the lowest.
Some types of loans require specific appraisal rules, like FHA, and VA requires your lender to use a particular appraiser assigned by them. Inspections are your choice. On a new-build you can simply wait until near the end of the builder's warranty on the house, usually a year, and bring an inspector in to catch any defects you have not already uncovered yourself and had the warranty department fix.
It's probably too late to bring a Realtor in to represent you, since you are about to close, but for next time, take advantage of Realtors' expertise -- it doesn't cost you anything and often can reduce your sales price.