Details here: https://www.familysearch.org/help/helpcenter/article/how-many-memories-photos-stories-documents-and-audio-files-can-i-upload
Anthony, there are 2 components to your question:
No limit — total memories one user can upload
1,000 — total memories tagged to one ID (person)
If you have contributed many memories, you may experience slow performance when you view & use the memories gallery.
In my experience, when the total number of memories tagged to a single ID approaches 999, no additional memories can be tagged to that person, but no error message displays.
It seems that private memories are counted toward the total, so the number of tagged memories you can see may be fewer than 999.
Anthony, you asked us regarding removing memories so I can create more space.
Please review the knowledge article listed below.
https://www.familysearch.org/help/helpcenter/article/how-do-i-remove-photos-and-other-items-from-an-album-in-memories The additional answers to your questions are listed above.
Thank you for using this wonderful feature.