I have only had one violin since I started, and only tried playing a few others from time to time. When I picked up other violins to play the only thing that was difficult to adjust to was the varying tone quality from one to another. Generally, the feel and placement of the fingerboards was not difficult to adjust to.
I have owned and played several violas in my time. Violas, more so than violins, differ greatly from each other. I found the adjustment from one viola to another to be quite a challenge. It seems funny now, but the first viola I learned on was one that was owned by my high school, and when I switched from the violin to the viola, I encountered no difficulty at all adjusting. Later, I purchased a Czech-made viola and didn’t like that there was a ridge with a drop from the G to the C string making it difficult to shift from the two lower strings smoothly or comfortably.