How does it relate to Scry-Buff-Teleport or similar strategies that initiated my concerns about mitigating the tendency of high level parties being able to go Nova?
It is somewhat difficult to Scry but it still works, the Teleport still works but that is probable your only spell at that level. It is 7th level I think. as for buffing, not a lot of that in 5th, you might have one or two buffs on a person. they can be powerful but they use up precious spell slots. a caster has less to less than half the slots a similar level in 3.5.
in PF 1st edition my 17th level wizard has 11 1st, 10 2nd, 10 3rd, 6 4th, 6 5th, 4, 6th, 4 7th, 3 8th, 2 9th
in 5th a wizard has 4 1st, 3 2nd through 4th, 2 6th and 7th, 1 8th, 1 9th with no real means to change those numbers.
that impacts buffing almost as much as the concentration rule which keeps buffing to 2-3 spells on each character at best unless you specialize in them.
I know I could elevate all those numbers but I could do that in both systems so the point of getting a great deal better is mute to me.
Now Nova is a different horse. In my game it was common, due to my style, for characters to nova. It was expected and just part of common strategy. The world as the characters experienced it was that they fought 1-2 things a day while traveling and usually had to deal with a few layers of protection to get to the big bad. It was my style and I adapted to it by having very nasty encounters and not being easy on them during them.
Dungeons being a little more difficult but characters knew going into a place / location to be more conservative.
For those that cry the players are metagaming my style, like I said this is viewed from the character's experience and it is what they learned to expect. We only have X number of firefighters in a city because we have X number of fires. This is experience they have learned from the real world, not the fire chief or city Metagaming the real world.
To address the original question there is a huge difference in 4 rounds of buffing in 3.5/PF and 5th ed. In 5th that is probably 3 wasted rounds.