727 noise from Reverse to Neutral and 3rd to Neutral when cold.

Slow into reverse IMO is a bad sign. When in reverse, all regulation of pump pressure is bypassed; it runs wide open at about 255 or more psi.
The reverse circuit consists of the L/R band,and it's servo, and it's adjustment;
plus the Hi-Drum (front clutch), and,it's clearances.
So this can be used to help diagnoses.
The high-drum is also used,together with the Forward-Clutch, to make "Drive" or third gear.
The forward clutch is used in all forward gears.
So, if second gear is not slow, then the forward clutch is OK, and
If the 2-3 shift is not slow, them both the hi-drum and forward clutch are OK.
So then we are left with the reverse system.
Now the L/R band and servo are also used to engage low gear. So if the N-L shift is not slow, then the L/R band, and servo, and adjustment are OK.
That just leaves the manual valve or it's adjustment; that is, the cable adjustment.

Now taken together with the buzzing noise, it may be that someone put the wrong sized ball in the hi-pressure relief valve, or that something is wrong with it; then they buzz. And if the pressure is not being properly regulated, then perhaps your pump is dumping most of it's oil back into the pan, and that could be why the N to R shift is slow. Now I'm not saying this is the problem, but at this point, This is what I'm thinking.

You can check the servo pressure and see. Just make sure you do the test when the issue is manifest, namely with cold oil. It should be 230 to 260 psi at IIRC 1000 rpm.