All the delegates have to support Trump on the first ballot if he wins today’s primary and goes into the convention either with 1,237 or very close. It’s all moot because he’ll already have 1,237 before the convention.
I’m pretty sure that we here in Washington state have the system where it goes by percentage per district so it might be a mix and mash rather than 100%.
And the democrats DO vote today as well - although the primary results for them have no say in how their delegates need to vote.
One of the big things is that the names are recorded as either democrat or Republican - so it gives a list of people to contact in the fall to remind them to vote.
WA polls close in under an hour.