Best tubes for Modwright Oppo UDP-205 and why? ...(6922, 5AR4, GZ34, 5R4GYS 5U4, 5V4)

Of the rectifiers you list I much prefer the 5U4 tube to the others.

I have a ModWright Hapz-1ES which uses the same 6922 tube output.  I'm using  sophia aqua 274B in the PS 9.0.  Huge improvement over everything else I've used.  more meat on the bones, air, you name it.  Surprising improvement from a rectifier.  I used the Telefunken 6922 tubes from Upscale for years and they are very good but can be hyperdetailed in a system that is otherwise highly resolving.  I prefer 1960s vintage Mazda 7308s in my system.  Resolving but not excessively so,. Very sweet,. Good bass, nice air and sparkle.   Just wonderful tubes.

Great advise.... But want to limit this to tubes if possible.

I have a heavily modded Oppo. Amazing what a budget component with quality hand picked parts upgrades can do.

But... you want to mod your mod? Out-mod the modders? Why tube rolling? Why not caps?

Seriously. Take whatever money you were thinking of blowing on tubes, put it into something known to work wonders. Total Contact, Stop Its, Orange Fuse. Stuff like that. Way better rate of return.