speaker installation question for the experts

I'm planning to upgrade speakers on all doors and add a bazooka powered tube. Keeping Package 3 HU. I viewed and founded a couple thread on speaker installation. Still have question before I start because I want to buy all neccessary parts ahead.

Must we used or make an adaptor Plate if I get 6x9 speaker for the front and 6.5 speakers for the rear? I was hoping to get a thin mounting depth 6x9 and install it directly like any other car I had before.

Dash speakers. Any issues if I just remove it and wire in a component tweeter from the front door?

Thx in advance for your advice.