6SN7s

about 10-15 dB

Fixed (negative grid) bias

I would stick to the classic circuit. Don't mess with it
unless you are familiar with designing differential
amplifier stages.

807s are great. The cheap Chinese ones aren't, but NOS
are still relatively easy to find. 6550s or KT88s
are even better--more gain, tougher screen grid.

How do you mean? It's a classic topology. But depends heavily on a good output transformer. Don't skimp on that.

In fact, if you want a really good version, I recommend the John Eckland designed KT88 amp project in VTV issue 19.
It uses Plitron transformers. I can attest to its excellence, having heard it (with a variety of classic speakers).

No that amp isn't on the Plitron site. Sorry, you have to get that issue of VTV. The owner of VTV expects to get paid, so support him and be nice.