A Thread ripper will have more than enough cores to handle unreal. Though I’m not sure about their peak clock speeds.
You might want to opt for slightly lower core counts with better speeds as unreal will not be using all cores at all times (I have a 5950x 32 threads and only time I saw full utilization was compiling unreal from source & that was only during parts of the process).
CPU probably depends on other workloads. If you do lots of cpu rendering then more cores = better but just for game dev you will see more benefit from higher clocks speeds on a daily basis.
Ram = the more the better. I opted for 64 gigs in my rig (ddr4). If you are making a new PC then I would look into ddr5 and check if the prices are reasonable their speeds are considerably faster then last gen.