ANSWER TO QUESTION 1
The models Barbero and the Santos I play are pretty similar to each other regarding touch (pulsación) and measurements, but they are slightly different from each other regarding dimensions and internal work of the top. One of the many reasons I like these guitars is because I can switch from one to another very easily. 20 years ago it took me a couple of months to feel comfortable with the change from a Conde 1974-Cypress to a Ramirez 1956 or to a Felix Manzanero-Rosewood for example. I didn’t like that part, because, just as a variety of colors are necessary in art, in my experience, different guitars give color to your playing and to your recording works. This is an important question because the easiest is to play your different guitars simultaneously the better.
ANSWER TO QUESTION 2
You can have a simple HYGROMETER like this:
*Do not leave this sensor inside the case, it should be outside in the room where you keep the guitar.
IMPORTANT: Use the humidifier only if the place is under 40% humidity (generally in winter time in cold weathers). You should re-fill it with water every 2 or 3 days.
Here is the link for the HUMIDIFIER: