Hello Monroe Arts Council,
Thank you for your question on how to use tables in BoldGrid. BoldGrid is a plugin suite for WordPress which adds layers on top of the traditional WordPress editor for pages and posts.
You can always add normal HTML and CSS within the Text tab. The CSS can be overwritten by using the Advanced Tab in the Customizer. There, you can add your own custom CSS and JS. This will supersede the other CSS in the theme.
As far as the TH and TD settings, these can be different for each theme depending on the intention of the design. You can always override that in the custom area.
You say you are having some issues with come changes taking place. Where are you placing these changes? What theme are you using? What specific changes are you making that are not working?
Kindest Regards,
Scott M