Gmail limits the size of email content to 102kb. This is a hard constraint that Gmail applies, regardless of what platform you use to send your emails.
When your email exceeds that limit, Gmail will place the following at the bottom of the email:
We have worked diligently to create the lightest email templates possible, along with other measures, to ensure that the emails you send aren't bogged down with unnecessary weight causing your email to clip prematurely.
In addition, when you are approaching the 102kb limit, beehiiv displays a warning that some users may experience a clipped email:
Your readers will still be able to view your content by clicking the "View entire message" link, but it's best practice to stay under that limit — or keep important elements near the top of the email where they are unlikely to clip.