Or is it still the same stats for all ratings?

read how stupid you are here: https://forums.d2jsp.org/topic.php?t=100800310&f=210

So gonna assume that's a no

All items for pvp bump to 450.
I guess it levels the playing field for casual players.
And makes it so in order to have the best items in pvp, you pvp.
No more pveing to get the items, i suppose some trinkets would be good from raid still though.

This.

I think your main question is, a ToP pvp Ranked player can ugprade more than a lower tier pvp player? Yes and no.

For RBGS, BGS, Arenas the gear auto upgrades to 450 ilvl. Any pvp items from conquest new season.

However for world pvp and world farming quests etc the ilvl of the items can be upgraded. And on this case you need pvp high rating to reach the maximum.