My experience with pre-orderes has been very limited, but good, so far.
I have pre-ordered a couple of MTH engines from a Forum Sponsor that turned out well.
I have pre-ordered several LC+ engines from my LHS that also turned out well.
My last pre-order is a Legacy engine from a Forum Sponsor that is scheduled to be shipped by Lionel in July, 2021. We will see how that one turns out. Arnold