P: Sync all Ecosystem Metadata with Classic desktop version

Workflow Question -  on syncing metadata. I am a new Lightroom user. Through lots of trial and error, I realized I needed BOTH Lightroom CC and Lightroom Classic which I now have. As many have discussed, and I have learned through painful experiences, both versions don't always play nicely with one another and are a bit of a disaster.   

For those using both Lightroom CC and Lightroom Classic, can you share the most effective workflow that you use?

Here is what I have figured out so far. 
1 - Download new photos to Lightroom CC ( I heard in a training, that if you upload to Lightroom Classic they will not sync with Lightroom CC).
2 - In Lightroom CC - rate all photos with stars and checkmarks, etc.
3 - In Lightroom CC - Add Keywords (After doing this in CC with 2,000 photos, and syncing with classic, I found out the keywords don't upload to Classic.) If I do this in Lightroom CC will the keywords be added to the metadata on the web? OR do keywords need to be done in Lightroom Classic, or do I have to do it in both places?
4 - Should I add the Title and Caption for my photos in Lightroom CC or in Lightroom Classic and why?
5 - Then Switch to Lightroom Classic and sync the photo's and then add the metadata, creator data, and location to all of my photos as this feature ISN'T available in CC and is only available in Lightroom Classic.
6 - Then add my watermark to all of my photos in Lightroom Classic, as this feature is also NOT AVAILABLE  in Lightroom CC.
7 - Image hardening? What do you use for additional protection of your photos?

From this point, what is the best way to get all of my images uploaded onto my website?
Do I try and do it from Lightroom Classic OR Lightroom CC.
Which keywords and metadata will the crawlers on google pick up when trying to index the images?
Will it pick up the keywords in Lightroom CC OR Lightroom Classic?
Should I even bother putting keywords into Lightroom Classic? Does anyone know these questions?

Is there anything in my workflow you would suggest doing differently or add anything?
Has anyone on here used the Plug-ins suggested above to sync their keywords or other data? I think it is called the Photographers Toolbox?

Any other things you would suggest as a newer user to Lightroom? Did I forget anything?

Any insights you could provide would be greatly appreciated!

I also agree that LR Classic and LR CC should do a much better job of syncing metadata. There's already a fairly popular feature request for syncing keywords specifically:
https://feedback.photoshop.com/photoshop_family/topics/keyword-bug 

Be sure to click Vote and Follow on that topic. (This topic shouldn't be merged with that one, since this one is about more than just keywords.)

Adobe has publicly indicated they have no intention of enhancing LR Classic sync. But if enough customers provide feedback, it's conceivable they'll change their mind. The last couple of user surveys had questions about LR Classic sync, so at least someone within Adobe is questioning the party line.  

This is not a real answer. There is NO reason we have to have Hierarchical fields. It makes way more sense to get keywords meshed than to get others only using CC. There are engineers who think creatively, but not often. This was done backwards! 

I am at least glad to know that the sync failure is through technical difficulties and not (as I had thought) a deliberate policy. The update from Classic to CC is fine for image changes and it can't be that hard to update metadata in that direction - it already flattens the hierarchy on the first upload. Coming back from CC (flat) to Classic (hierarchy) I can see might be harder. SmugMug ad Flickr both do seamless metadata updates from Classic, and now they are one, the attraction of CC diminishes if you can update metadata. 

This is really annoying.  Neither labels nor keywords sync, which I use extensively to organize my pictures on the desktop.  I simply want to be able to filter and browse, and do some light editing on the go, but I NEED these existing organizational tools.  But I suppose I will just have to go through tens of thousands of pictures again and re-tag and label just because Adobe is lazy?

And why are labels being dropped again?  This is not how to you move forward, Adobe.

I'm glad to see others share my sentiment. Has anyone found any sort of comprehensive & clear listing of what fields sync & do not sync that Adobe has published as part of their technical support services? Poking through forums & crowdsourcing technical support is incredibly inefficient. Thank you all for chiming in!

Totally agree, John. I get that keywords might be a harder thing to deal with, but location data? I don't understand that one at all.

I stand corrected, Jim. Even less excuse for failing to sync the location fields!

John, oddly enough the GPS value does sync, just not the 4 location fields.

I agree with you. I wish Adobe would adopt a more pragmatic policy than the "no more than now" line which syncs title, caption, adjustment metadata, flags and ratings but fails to sync other single value fields such as 4 location fields and the GPS value. Keywords are understandably difficult - hierarchies, synonyms, do not export etc - but the existing single value fields sync reliably and it's hard to believe that the others are any more difficult in principle. If you can sync all that complex adjustment metadata, you can sync 4 or 5 little text fields.