@jhuynh Thank you for reaching out to Microsoft Q&A.
- The support for popups was added recently in self hosted portal #1893 and it is currently being rolled out in managed portal version. If you can elaborate more on side navigations with example and screenshot, it would help us understand better.
- You can navigate to Styles page in the developer portal (Global Styles- Styling Guide) and choose/upload font and select Typography for form controls such as Label, Text box, Buttons, links etc. However, this applies at the global level, and we are working to enable more local styles in widgets so that users will be able to override global styles (see comment). Unfortunately, ETA is not available at the moment. Here is the sample textbox color and button color change in the signup widget (applied from Global Styles).
If you see some styles at the global level not applied in widgets, please share an example with details for us to review or feel free to open an issue in GH repo.
Also, I would like to let you know three options that we have to extend portal functionality and please review doc for detailed info.
I hope this helps with your question and feel free to reach out for any questions. Please 'Accept as answer' and ‘Upvote’ if it helped so that it can help others in the community.