OP, since you have so much flexibility, I would take a blended approach. I'm not sure of your risk tolerance, job satisfaction, current asset allocation, income, age, or income stability, but you sound like you have a long time horizon so you should definitely have some exposure to equities. If you have income and a pretty secure job, this is a bit like having a bond - regular payments that hopefully continue as long as you need them (with a high NPV that probably dwarfs your other assets).
So, depending on risk tolerance, definitely put the 20% down and maybe more if it would pain you too much to lose money in the market in the short term, causing you to jump ship after a sell-off. But, by avoiding a mortgage before retirement, you are betting against history, that every rolling 30 year period up to today has had a real return that beats your mortgage expense (especially if you can use the tax deduction).
You can bet against history, I have seen some economists getting concerned that we are in uncharted territory with low interest rates as well as high market valuation, but if you lose this bet then the person you could have been (experiencing ~4% higher delta returns (market vs. mortgage) for 30 years) will be almost 200k ahead on that 60k lump sum investment, vs. putting the theoretical mortgage payment amount slowly in the market. ((For example, a 60k lump sum for 30 yrs at 8% nominal return = 604k vs. 3540 yearly mortgage payment, 30 yrs, 8% = 433k))
Another benefit to having a mortgage while you are working, it forces you to live within a reduced means. When you retire, you should be in even better shape to make the decision to pay off or keep the mortgage. I lean toward paying it off, since it will be an annoyance and so that you don't have a fixed liability when your income might be less predictable. Again, you don't want to have to sell equities during a down market. I also understand arebelspy, I've never paid off a mortgage because it's like having a pile of money that doesn't throw off any interest, dividends, or give you easy access to principal. A mortgage, for working people, is like someone loaning some of your future income to you to invest.
For extra credit, I'm partial to Another Reader's idea for a lower duration mortgage than 30 yr. It lowers your interest rate, lowers overall interest paid, and increases the tax deductible interest paid, especially in the early years. You can try to match the duration to your expected retirement date (10 years).
By the way, you are in great shape having the 80k liquid and planning on living in an 80k house!