With hormones the two dangers to look out for is liver damage and blood clots. Liver damage is monitored with regular blood test and blood clots happen because of known risk factors. Both issues can be controlled by reducing dose levels in people at risk.
Blockers were intended as blood pressure medication with the secondary effect of blocking hormone production. In our case the primary goal is to reduce hormone production and the secondary effect is a reduction in blood pressure. If low blood pressure is an issue then blocker might present a problem.
When I transitioned, blockers hadn't been discovered yet so we only took hormones and in my case, I suspect T production wasn't fully shut down. My feminization was better after SRS but even without blockers I did develop a feminine body. One could still transition without blockers but the results might not be as good until after SRS. An Orchi would also be a solution to the lack of blockers but if limited feminization is acceptable, then you could wait until after SRS to finish off the feminization.