You are more likely to be killed outright by line voltage than by high
B+. 70 years of Amateur Radio statistics-most of which time hams were
mostly builders-bears this out.

Design commercial products with interlocks like transmitter
manufacturers did for years and if you are a DIYer buy and/or build
proper safety equipment and use it.

Tube amps running 1 kV and above are the best sounding and most
reliable-they either are built properly or fail spectacularly and in
short order-way to get substantial power. The 812, 813, and a bunch of
other tubes out there can sound great and give good service. You have
to put some build cost in the amp, which is as it should be.