If I were to sum up "Trumpism" in a sentence as far as it relates to what kind of party the GOP is/will be, I would say that the Trump GOP is a party that welcomed the Ross Perot Republicans back into the fold and forced the movement conservatives to tolerate them.
The days of the race for the GOP nomination being a litmus test for "who's the most conservative" are over.
Isn't the GOP nomination a "Who is the most Trumpist" litmus test now though?
Not really, no. There is more diversity in issue positions amongst Republicans these days. As long as the candidate endorses Trump, there is wiggle room for issue positions.
At one time a guy like Jeff Van Drew would have been primaried out of office even after switching parties due to being recruited for being insufficiently conservative. The GOP is over that now. Van Drew is a moderate Republican, but he'll be OK so long as he supports the national ticket (which he does).