Basis set confusion

[Matthew]

Hi all,
I'm a little confused about the selection of basis sets for cp2k. I've
been using the basis sets in cp2k/tests/QS/GTH_BASIS_SETS to some
success, but I have some questions.

Question 1: When I use the DZVP-GTH sets, it works nicely. When I try
a better basis set (QZV2P-GTH), the SCF no longer converges. Why is
this and how do I resolve it?

Question 2: What are the augmented basis sets? Would I use them /
instead/ of the normal basis set? When should I use the augmented
basis sets?

Question 3: Why are some elements not available? Their
pseudopotentials are in the POTENTIALS file, but there is no GTH basis
set. For example, Titanium. It is available only as DZV in the tests/
QS/BASIS_SET file. Is this sufficient?

Thank you so much,
Matthew