I've used oral and injectable. Can't say one seemed better than the other for me, but I settled in on injectable. I think that dosage would probably be a wise place to start. I can't say i have first hand knowledge of the toxicity, but there's a bunch of claims it's one of the most toxic steroids you can take, and based off how I felt on 1mg, I think you'd definitely see results from something even as low as 150-250mcg. It was definitely a fun compound to use.
So I can't speak to the muscle building abilities, really just crazy strength for me, as when I did a cycle nothing crazy happened physique wise. and I shortly after i fell in love with MENT which did give me radical results, so I left MTREN behind, but I read alot of anecdotal info confirming what you're saying.