RCP has been a decent barometer the past few election cycles. It averages name polls with decent samples that use either registered or likely voters.
I think it’s still fair 4 months out to be using registered voter polls, but not for much more than another month or so. Registered are fully able to vote legally already, it’s just that not all of them will. The pollsters should be making strides in refining down to likely voters as these people indicate whether they will or won’t participate this time around.
I agree, register voters should not be sampled after the Conventions.