Well first off I want to say that test U should be in castor oil if your looking to get the true benefits out of it. Test u in other oils absorbs faster and isn't the same as it in castor oil. And this has already been proven by science in trials because I know there's gonna be a bunch of people that say the oil doesn't matter but it does. We have had this argument for years on here and people produced proof to show the oil does matter.
The difference between the esters is basically your going to convert more estrogen on test u than e or c most likely. Usually longer eaters convert more. And the time differences. E and C are shorter and need to be injected more often than U. But most people prefer E and C over U.
But as for dosing, you have to feel what works good for you and get labs done to see your levels. Nobody can say you need 200mg or something. They can give you like an estimated range what they think you'll need but nobody on here can say you need this much and it's gonna work for you. But depending on your age I would try to be in the 600-900 range for like proper trt.

A safe starting number is a mg per lb of lean muscle mass. Get bloods then go from there.

180mg - 60mg MWF. Not really aiming for a serum number for keeps me about 1000ng/dl with an E2 that doesn't require an AI. Test Cyp or Enanth is generally utilized by most but some clinics prescribe ridiculous protocols using Test U every 2 weeks.

Gotta find what works best for you though