[Android Central Question]

I'm coming from iOS, so apologies if this question has been asked a load of times already.

I have a pixel 2 XL and re-learning my daily stuff. It's all good, but there are a couple of things I'm struggling to get my head around.

The First thing is - Instagram and Google Photos - I've got all of my pictures there (in photos), but I have to follow a line of about three steps to get to the full photos library if I want to add a picture to instagram.
I've tried setting photos as the default app, but it's not giving me the option to do that.
I can't find a gallery app to uninstall or deselect as the default.

So I'm running in circles just to get instagram to see the photos library - it's a bit of a hack.

While I'm at it there doesn't seem to be too many options to set defaults for other apps like email (I'm using outlook) and so on.

What am I doing wrong? I'm tempted to run nova launcher and an iOS skin, but want to not fall at the first hurdle!

Can you help?