A family of Microsoft word processing software products for creating web, email, and print documents.
First of all, update Office. The version you cited [16.107.4] is 2 major updates behind. Version 16.109 is current. That, alone, may resolve the program.
There is no setting in Word to specify the window size or position. Normally, documents do open at the size & position at which they were last saved & closed The one exception [unless changes have been made in System Settings] is if Word is already in Full Screen or Focus View. Those are viewing modes, not document settings. If a document is open in either of those Views, other documents – including new ones – will open in that same View. The UI provides no way to open documents in either of those views otherwise even if the View was in effect when the document was last saved & closed. IOW, documents cannot be saved in Focus or Full Screen View.
Note, however, that windowing operations are owned by the OS & Tahoe has had a number of windowing maladies. It's possible that on has returned in this latest release. If so it will require an update from Apple to provide the remedy.
Also, the view mode being used by one program should have no effect on the viewing mode in others.