In my two amps that use 12BH7 I can't say that I have noticed a difference between tube brands or NOS and new.
12AX7 is another matter entirely. Long subject that has been discussed and rehashed before on this and every other audio forum. There are too many variables to give you a specific opinion. What amp, speakers, music, budget - all important data points and considerations. Some sellers; notably Brent Jessee and SND Tube Sales, offer picked and graded used tubes of may NOS 12AX7 types. Some of them are pretty darned inexpensive. But yourself a small selection and try before you buy.
12AX7 is another matter entirely. Long subject that has been discussed and rehashed before on this and every other audio forum. There are too many variables to give you a specific opinion. What amp, speakers, music, budget - all important data points and considerations. Some sellers; notably Brent Jessee and SND Tube Sales, offer picked and graded used tubes of may NOS 12AX7 types. Some of them are pretty darned inexpensive. But yourself a small selection and try before you buy.