Minor design tweaks/fixes in overview section

[data-sync-user]

This includes:

• Misaligned columns in hypothesis section
• Branch titles + population size should always be on 2 lines
  • Also make them larger
  • Show full population size when hovering over
• Remove subtitle bar
• Update branch screenshot placeholder
• Remove inner cards and allow content to fill outer card
• Doesn’t need to be collapsible

┆Issue is synchronized with this Jira Task