Give this little list a look, maybe there is something in those docs that is causing the issue. I'm not fluent in this type of stuff but maybe there is a compatibility issue, especially on docs with lot's of custom formats. Bottom of list there is a few things.
Compatibility changes between versions - Word
Couple ideas... Safe mode uses a basic vga driver that does not implement hardware acceleration. So since its snappy in safe mode I would suggest changing hardware acceleration within Word in normal mode. Hardware acceleration is a complex high-speed dance between windows, your graphics driver, and your graphics hardware and it is known to stumble in many applications that use it. I think its in File > options > advanced. If its checked, uncheck it. If its not checked, check it.
Another thing that comes to mind is your hard drive. I understand that it is not fragmented. But if its 95% full, that can cause an issue as well.
Another thing is safe mode drivers are more basic than normal mode drivers and may use only a subset of each device's hardware. So you can have a device not working quite right in normal mode but its fine in safe mode. To check your normal mode driver status do start > run > msinfo32 > components > problem devices. Hopefully its blank.
Windows Aero use a lot of resources
Try to use a Windows classic Theme
Control Panel\All Control Panel Items\Personalization - Basic and high contrast Themes - Windows classic
I have similar computer at work as OP and this type of computer is perfectly capable of running everything OP does, but it needs maintenance after a while: clear all the garbage, clear all caches, delete all the Win updates leftovers, all MS spying, I mean customer experience etc etc. There are programs like CClean, DISM+ and others that can help with this task, but topic is too large in scope for this forum. Another option would be clean reinstall of Win7 and all software. BTW MS office is resource hog like no other and there could be some rogue programs/processes, so task manager should help identifying those. I just had same thing like OP: boot up alone would take 4 min and computer would hang when typing, I clean it up and it runs like new, but it is multi step process that requires some time and it would be redundant without actually being there. BTW I've never seen AERO itself creating problems, usually Windows will disable some of it's features automatically if hardware is weak.
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