Your first question is already in the mod. If you set the mod setting: "Swimming speed" to 1 and leave "Deep water swimming speed" as it was then only deep water will slow you down.
The second one I'll have to think about how I'd want to achieve this. Currently I can't just make the player be able to swim but not have vehicles be able to swim this is a limitation of factorio. However what I could do is for instance make the vehicle take damage and explode when in the water. Another way possibly is to just flat out eject people in vehicles when in water but this has other issues as ejecting does not always work as expected. I'm leaning towards making the vehicle taka damage so that the player still has a tiny window to try to escape the water death of their vehicle. I'll post back here when I've decided what to do.
