Do I need to switch to Z-Wave JS?

The Zwave gateway wont have any impact on Hub Mesh. You can have one on Zwave JS and the other on ZIP no problem.

Aeotec smart switch 6 does not switch correctly using z-Wave JS and remotec scene master never changes from pending even when power cycle unit and hub an wait for 1 week

Did you try excluding and then inclluding again or manually teiggering the re-interview?

When I finally bite the bullet and upgrade my C8 to a Pro, I'm really looking forward to all of the shenanigans with my various devices...

I did try re triggering but did not exclude/ include, tried this a few months ago but as I don’t have non production environment I can not continually keep attempting this task, easier just to change back

I have several under-sink leak detectors. Do I need to somehow wake them up to get them to rejoin the network after updating to JS, or will they find the network on their own?

And, is there a screen in my C-8 Pro where I can see if they are still present and accounted for, so to speak?

Are they not listed under Z-wave devices in Z-wave settings?

They show but all say "pending" while the powered devices all show with a check-mark.

They haven’t woken up yet. You need to wake them to get them out of pending.

Or just wait for them to wake up on their own.