I don't mean to put you off Teles completely, you just need to appreciate their deficiencies.
The x1.4 is pretty much always OK and will give good results; the loss of contrast can easily be pulled back in post.
see
HERE and
HERE
The x2 tele is problematic unless you have a really good lens but again contrast can be pulled back in post.
See
HERE
The lens is crucial and IMO you need a good prime to make them worthwhile.
Sony teleconverters are compatible with the following lenses.
Minolta - AF 200 F2.8 G
Sony/Minolta 300mm F2.8 (SAL-300F28G)
Sony 135mm F2.8 [T4.5] STF (SAL135F28)
Minolta - AF 400 F4.5 APO G
Minolta - AF 600 F4 APO G
Sony 70-200mm F2.8G (SAL-70200G)
Sony 70-400mm F4-5.6 G SSM (SAL-70400G)
They may work with other third party lenses, I can't say.