RMD

A plan is terminating in 2025.

If a participant is over 65, do they have a Required Minimum Distribution (RMD)?

What if funds are rolled over into a 401 (k) plan?

Sorry, I made a mistake.

I meant over 73

If they have met their required beginning date, then, yes, they have to take their RMD before distributing the rest of their account. 

Can be paid out concurrently but in two portions - RMD not RO-eligible and not subject to 20% w/h, and then a RO-eligible LS which is subject to 20% w/h to the extent not rolled over, either to another plan (401k as you mention) or IRA.