Bright day
There has been several threads on the matter.
Well if the PoD is that one battle, then I am not sure that Ottocar II would be able to turn whole Empire for himself.
The lands he acquired for dynasty would be returned I think.
As for internal state of Bohemia: it would be much better off without the disasterous regency by Brandeburgers and the latter regency of Queen Mother's lover Záviš of Falkenstein. The mental health of Ottocar's sucessor, Wenceslaus II, would be better and he was pretty brilliant OTL (and concieved before the PoD). Plus the silver mines of Kuttenberg are about to reach it's most productive period.
For its expension, if the infamous flying insect do not cause havoc, the Przemyslids may as OTL reach for Polish and Hungarian crowns. In OTL they controled about third of Hungary at best, and their rule in Poland was plagued by incessant uprising. But ITTL their powerbase is quite larger, which could leave them with larger pieces of these kingdoms, if not all of them. Of course it may all be butterflied away.
Miscellanous: If they maintain their hold on imperial title, they will not eye papacy in Avignon with delight. Speaking of French, there is not going to be Charles IV, with his inferiority complex at France- thus the establishment of university in Prague may be delayed. If this affects other universities in Germany I do not know.