I use the Nikon F 105mm on the FTZ with a Z8 camera. Previously I used it on my D300, D800, and D850. (I eventually broke my original lens and replaced it with a Like New used copy) It remains razor sharp and super-fast with the Z8. I don't think anyone would complain about sharpness or slow focus with this lens.
That said, if I didn't already own the F-mount I would buy the Nikon 105Z lens if your primary camera is a Z-system body. I've not used it, but the evaluations all claim that it is a bit faster and sharper than the F mount. However, the improvements are marginal and not easy to demonstrate. It is going to be a bit lighter and smaller than the F-mount+FTZ however. If you already have the F-mount, it's going to be an expensive upgrade at ~$1000 for the lens and possibly a new Nauticam port or spacer. A very optional upgrade with a low cost/benefit ratio.
Long ago I used to shoot the 60mm on DX cameras like the D300. It was a natural fit on that format. When I moved to FF the 105 drops into that comfortable slot the 60mm used to hold. I rarely use my 60mm any more as a result, it is just not as good. The difference from 90mm to 105mm is not significant and I don't think it's in the favor of a 90mm format.
I would be interesting to see a head-to-head with Tamron 90 and Nikon Z 105mm. If nothing else, the F16 limit of the Tamron would make it an uphill climb against your Nikon options. The Sony 90mm is not universally loved, so the Tamron probably looks like an attractive option for Sony Shooters.