First of all 250mg of any Testosterone is not a TRT for all, but maybe 1-2% of population and even then they should probably inject more often and lower their dosage!
Nobody can say, if you gonna need AI. I would require anastrozole 0.25mg twice weekly for this. Another example is on TU 250mg (undecanoate ester) I need more, something like 0.25mg eod. As you can see it's differrent between esters not to mention everybody is different.
Please don't copycat the above, you are not me, it might be too much for you and lower your estrogen too much. Blood work will tell you all you need to know.
As for injection frequency when it comes to Sustanon ester it is ideally eod, or at least 3x per week due to propionate and phenylpropionate esters.
Overall, I would recommend different ester of choice like enanthate or cypionate, even propionate. Basically single ester causes less side effects and more stable Testosterone blood levels, not to mention estrogen. Fluctuations are not productive.