There is a oral form of trenbolone called methyltrienolone or metribolone. And no, it is not non-liver toxic. It is 17 alpha alkylated like the most of orals are.
The choice of the ester depends on your cycle. If you are going to keep your cycle short and using short esters with tren, then opt with tren ace.
If your cycle is long and you use long esters along with tren (test enth, deca etc..), then go for tren hexahydrobenzylcarbonate or tren enanth.
The reason why is short esters leave your body faster than long esters. And also if you are pinning other short ester compounds frequently (ED or EOD), then you can pin tren ace with other compounds as well. So that your pinning pattern will be matched.
Tren is tren, it doesn't matter whatever the ester is. Esters only affect the active-life of the drug and your pinning frequency. Use what suits you best.
I would not bother with prohormones at all, just get the tren itself and stick with it.

You didn't mention your stats and cycle history. Tren is no joke, you should already have run cycles before using it. Running cycles before tren will get you used to exogenous androgens and educate you about your estrogen sensitivity, side effect management and most importantly HPTA. At this point, you should already have known your PCT protocol.