Good evening Sangho,
In view of your requirements and they are legitimate, it is always difficult to advise someone, the tastes and needs differ from one person to another,
I saw the answers that were given to you, there are also other "good" brands like MAUGEIN (factory in Tulle, France) the Octavia model in 96 low would suit you very well,you can also find the brand ACCORDIOLA (which was installed in Sarlat) in second hand they are very good accordions, in more recent brands you have the accordions BONIFASSI and EVOLUO, you will find all this in the search engines.
Precision for the big musette sound from Auvergne, it has nothing to do with the brand but it is a type of tuning, it is in this case what we call a three voices musette, for that when you buy an accordion you must absolutely try it to hear the sounds, knowing that a re-tuning is always possible, foresee a budget quite consequent of the order of 600 to 1.000 € according to the models and their state.
Good luck in your research and especially bravo for your interest in this beautiful instrument,
NB look also at the "digital" ROLAND, BONIFASSI, CAVAGNOLO, among others, you will find beautiful opportunities and there you will have a plethora of possible sounds (without retuning anything !!!!)
Sincerely
Jean-Pierre