Jack Elliano has a direct Coupled 300B thats been in my folder called "my first 300B" schematics for some time. Just throwing it out there because it is so simple and that multi tap resistor sure makes it easy to trim the operating point for a direct Coupled amp. Ultrapath cathode bypass. 700 V is high for a beginner like me, but I'm careful. 300B should love 700V. I have a One Electron OPT waiting to be used, but Id order the 60H chokes from Jack. Then later get some OPT's from Jack as well. I think DRD is Jacks abbreviation for "Direct Reactance Drive".
Electra-Print.com 300B DRD Audio Tube Amplifier
I build several amps inspired by Elliano's DRD amp using his AC8037 plate choke a decade or so ago using an assortment of driver tubes. I really liked the E180F (triode connected) as a driver using LED bias. The driver needs to have a cathode current of <15mA to use with the choke. I never made it with variable resistors, instead I used them to dial in the various voltages and replaced them with fixed resistors.
With the DRD amp, I have never used a power supply voltage over about 500Vrms because that's what my Electra-Print power supply transformer gives me with a capacitor input supply. I agree it is safer than 700V, but not by much. It also means that one can use 600V Wima MKP4 capacitors.
A 300B amp with the 500V plate supply will have a P-K voltage of about 300V with another 125V for the driver tube. I was not able to drive the 300B with my setup to more than 5W because of the low B+. This was the first of many direct coupled amplifier and it convinced me that direct coupling had some benefit to sound quality.