buy JR pas or regular tickets?

we would like to travel to Japan in January 2025 (2 adults). we are planning our trip, but are not yet sure if buying a JR pas (1 week? 2 weeks?) is cheaper than normal tickets. Can you help us? Where would JR pas be applicable? Is JR pas handy in the cities as well? Thank you!

plan for now is:

ma 20/1 osaka
di 21/1 osaka
wo 22/1 osaka
do 23/1 koyasan
vr 24/1 hiroshima
za 25/1 kyoto
zo 26/1 kyoto
ma 27/1 kyoto
di 28/1 kyoto
wo 29/1 matsumoto
do 30/1 matsumoto
vr 31/1 jigokudani
za 1/2 tokyo
zo 2/2 tokyo
ma 3/2 tokyo
di 4/2 tokyo