Depending on your pace you could get in 10 days from Porto to Santiago but that will be rushing and long days of walking.
Here some stages
1 Porto to Vila do Conde 32 kms
2 VdC to Esposende 24 kms
3 Esposende to Viana do Castelo 22 kms
4 VdC to Caminha 30 kms or to A Guarda 33 kms
5 Caminha to Baiona 26 km
6 Baiona to Vigo 20 kms
7 Vigo to Cessantes 23 kms
8 Cessantes to Pontevedra 17 kms
9 Pontevedra to Caldas de Reis 20 kms
10 CdR to Padrón 20 kms
11 Padrón to Santiago 24 kms
I should advise you take the teain to Viana do Castelo and walk from there
In Viana we had good experiences with pensão Laranjeiro ( not hotel Laranjeiro that's a different one) the owners, a young couple walked the caminho themselves.
In Caminha we stayed in a guesthouse opposite the trainstation. Not special.
In Baiona we went to the tourist information and they advised a very nice guesthouse. We loved Baiona.
In Vigo are hundreds of cheap hotels
Cessantes I advised. Although you do not like albergues, there is a very nice one,
O Refúxio de la Jérezana . The owner ,a nice lady can cook you a nice meal and a breakfast in the morning.
In Pontevedra are many hotels and guesthouses
Caldas de Reis dito There is a nice one, o Cruceiro but they did not react on my emails the other day so we booked another one for our next caminho
In Padron are several hotels and Guesthouses.
In Santiago are so many. Just look at Booking.com
I have no experiences with forwarding of backpacks .