Just put down 20% and get a 30 yr fixed -- you have 400k to spend. Make sure there are no big expenses on the house. Dont buy a cheaper $380k house and get a second, dont get any more loans at all. Get a first mortgage that has payments you can make for 30 years, do the calculation up to a daily basis. Example: $1717/30.
Make sure it is an absolute fixed mortgage with all fixed payments. No 2 year, 5 year, grace/fancy pants payments. The mortgage that is sold (maybe to a third party) is an absolute fixed annuity, and simple to understand annuities will be in demand soon, so your mortgage will be in demand. The point is that you should go with someone you trust, like a local bank, or a bank you have your checking and savings at. These companies are rare but they exist.
Dont go around pre-qualing, these companies all sell your info into the world of spamfinance. Just go with the credit union and make sure YOU understand what the hell is going on, thats all that matters.