[bkury]

- skin works smoothly, awesome job! even in 4K

That's good to hear! I don't have a 4K display, so I can't really test it. I was a little bit worried about 4k performance because this skin doesn't upscale from 1080p to 4k but instead it renders the GUI in native 4k.
(Still, I'm not sure if you can tell the difference between 1080p upscaled and native 4k because most artwork isn't even 2k. Feedback on this would be helpful)
 

- in alpha release, there was an option to Display / Hide movie name on the panel view, is this available?

Yes, this is still on my to-do list but there are some things I have to work on first before I can re-implement this feature.
 

- Widget : would be great to have an option to display On Deck only or Recently Added Only or both.

Are you talking about configuring every single widget individually or would it be enough to hide "ondeck & recently added" widgets based on content type (e.g. hide all recently added widgets if widget content type is movies) ?
 

- Is there a way to show Add On section in the in sub menu instead of menu?

Not yet, but very easy to implement (added to my to-do list)
 

My main issue comes from the On Deck and Recently Added loading time when activating the hidden widget. It might take up to 20 seconds to actually load it (and not every time), the recently added arrives first, then 10 seconds later the On Deck arrives.
I haven' tried on a different skin yet, so I will make additional testing to see if it's coming from PKC or the SKIN. Edit : Yes, it seems there are some lag issues while loading the On Deck from Plex.

Yes, when it comes to PKC "Recently added" widget will always be faster than "In Progress" widget because "recently added" data gets fetched directly from the local KODI database while "In Progress" data needs to be fetched from your plex server. Unfortunately, there is no way to replicate the PLEX "on deck" feature, which is a combination of "In Progress episodes" and "Continue show/season/episode", with KODI's filter rules. (A KODI feature request would be required to add the missing filter rules)

However, you might improve the load times by changing the maximum number of items to be fetched:
PKC Settings --> Appearance Tweaks --> Maximum number of videos to show in widgets --> change from 30 to 10