I mean, what do you want to hear. It is NA PTS server so that automatically makes it impossible to compare any experience with performance in crowded zones, PVP or literally anything for EU players.

As a NA player I can say that loading screens are much shorter when going into populated areas. Also fps is higher. I have not tested PVP though. For me it is a huge improvement.

I wouldn't say there's a ton but there is definitely forum post out there which speak toward improvements that can be done by players client side. The majority of the player base which has done these improvements seems to have minimal impact dps wise. The primary problem is & will always be server & network performance on ZOS's end. This will always be a problem unless some decides to spend more money on the servers, not going to happen, or there is a population drop, likely.
However, a population drop will only mean they will decrease server space/capacity & it will be just as terrible once again.
The only option is for someone to buy them out & do a better job or give them tons of money & "maybe" they'll upgrade a little; although it's unlikely.

When I'm near a decently large fight in Cyrodiil my ping fluctuations are between 110 - 700
It doesn't take but maybe 5 raids worth to hit terrible lag in Cyrodiil.
There were 3 EP raids & 2 AD raids, not even entirely full 24 mans, probably around 10-15 man groups each at less than 100 people total fighting around Alessia.