How do we install trim/door casing/arch the nicest way here?

[KristinU]

How do we do this in the best-looking way?

Our house is old and a bit crooked in several places. How do we make it look straight, at least visually? Should we remove the panel currently in the opening?

On one side, we have paneling (the darker color), so unfortunately, there's no option to smooth it out with putty and skip the trim.

 

[Pappa1986]

How do we do this in the best way?

Our house is old and a bit crooked in several places. How do we make it look straight at least? Should we remove the panel that is currently in the opening?

On one side, we have paneling (the darker color) so unfortunately, there is no option to spackle evenly and skip the list.

Tear down, put in laminated pine, paint or alternatively put in mdf.