Is my logic board salvageable?

It’s hard to say because the shields obscure essentially all of the board. You have to remove the shields to properly evaluate the chances of recovery. It doesn’t look too bad but sometimes minimal damage still causes maximal issues. Other times the phone looks horrendous and it turns out needing only a light cleaning. With water damage, you never really know.

Most shops will only work on the phone to save the data and you should have that expectation as well. Water damaged phones tend to have stability issues and develop other issues later on.

The proper (DIY) way treat a wet phone is to do the following:

• Open your phone and remove the logic board (follow this guide)
• Inspect the logic board, especially around the connectors and look for corrosion.
• Inspect both sides of the board. Unfortunately, most of the board is covered in shields. That's usually where the damage is occurring.
• Put your board in a container with >90% isopropyl alcohol and let it sit for a while.
• Use a soft brush, like a toothbrush and lightly brush away any corrosion you see.
• Rinse in alcohol and repeat.
• Let it air dry for a day.
• Re-assemble and hope for the best.