At which sampling frequency and resolution should I send you my tracks?

Of course, the highest sampling frequency and resolution are, the best the quality is.

But you should keep in mind the fact that, to have a 50 tracks operating at 196 KHz / 24 bits,
you'll need a war computer. The best for your system is not to be "on the edge of crashing"
when you are performing your final mix.
So it's up to you to find the right balance.

Working with 24-bit resolution is preferable during sound pick-ups because you will get the
best signal / noise ratio as well as a larger dynamics track.

Once mastered at Master+'s, your files will put in a Cd format, 44.1 KHz / 16 bits.