Is f/6.3 too slow for wildlife?

It is a stop and a half slower than f/4 super-telephotos, so you lean more on higher ISO or slower shutter speeds. Modern full-frame sensors and the lens's stabilization make that workable in daylight, but dawn and dusk shooting is harder.

Yes. The whole point of the f/6.3 design is a shorter, lighter barrel than f/4 600mm primes, and the built-in stabilization helps steady it. Long sessions are still tiring, and a monopod helps for waiting on subjects.

Does it work with Sony teleconverters?

Sony's E-mount teleconverters are compatible with select G Master lenses, and this 600mm is designed as a G Master super-telephoto. Check the specific converter pairing before you buy, since reach and aperture both change.

How does it compare with the Sony 200-600mm?

The 200-600mm is a zoom with more framing flexibility and a similar maximum aperture at 600mm. This prime trades that flexibility for lighter weight, G Master optics and faster focus response.

Is it worth it over an f/4 600mm?

If you shoot mostly in good light and carry your gear on foot, the lighter weight matters more than the extra stop. If you shoot indoors, at dusk or need the shallowest backgrounds, the f/4 lens is the better tool.

What comes in the box?

Expect the lens, front and rear caps, a lens hood and a soft case, along with the tripod collar. Check the listing for the exact bundle before ordering.