Always try to keep the video file smaller than 1GB (max 2GB). However, it is advisable to keep the video file size as small as possible to minimize the loading time. (it is also a good practice to compress the video file before uploading it to Systeme io)
Equally important to note is that bigger file size will indirectly slow down page loading, affecting the page’s core web vital. As a rule of thumb, keeping video 200MB max will optimize the loading and page’s core web vital.