To help, I'll package up a few screenshots of what I'm doing and why I'm doing it - might help others too.
I think that will surely help. Also, putting together the steps you are doing to create those cards before you share the page as well as Sharing permissions set on the source layer, sharing set on the shared page wol d be good information for me to try it out.
Eg; manually type in desired dimensions to create a card.
Not sure what you exactly mean by this but Insights follow the drag and drop approach to create cards, and you can change the variables after the fact by selecting the dropdowns. But there isn't a way to type things and create cards unless you are using the python/R Scripting module.
is there a way to removed the padding around a card
I don't believe we have padding around the cards. There are many creative ways to go about the presentation you can choose to remove the background or set the border to No borders from the card style.
You can also show or hide the card headers to make the card feel like floating in the work area
If you more questions about styling let's create another thread and keep this topic specific to the initial question.
Thanks,
Akshay Harshe