I own the Z 24-120 since I own a Z camera. It is the most used zoom lens on my Z7II. It has seen dust, rain and a lot of bumbs in trains and busses.
The range gives you most, what you need during the day. The additional programmable ring makes it easy to modify exposure.
You still can carry it with the camera on a strap, hanging on a side under your arm.
A choice I would make again in the sense to have my complete "light" travel kit: Z 14-30 4.0, Z 24-120 4.0 and Tamron Z 70-300.
An alternative imo would be the new Tamron Z 35-150mm 2.0-2.8. All the reviews I´ve seen so far are superb, but it is bigger and doesn´t go wider than 35mm, but here with aperture 2.
No idea what Z8/9 are doing, my AF with the 24-120 in my Z7II is not as fast as f.e. FTZ with 1.4 58 or the Z 2.0 40mm. It might have to do with the inside mass of the lens, but I think it has as well to do with the light coming to the sensor. In the evenings and under bad light conditions camera and lens are not, what i would call a reliable team to get a fast shot under any circumstances. Here my 1.4 58 lens shines in speed (as well as in the result)
As an addition to your primes I recomment it, but test the Tamron as well, if you have a chance.