So if the house you both live in is owned as joint tenants, if one of you goes into a care home while the other is still living in the house, then the house doesn't get taken into account when calculating contribution to care home fees. So the one living at home gets to continue living there and it isn't sold off by the council to reclaim fees. If the surviving spouse then wants to downsize, they have the full value of hte house to spend, or spend part of and put the rest in savings.
However, If one person from the marriage dies and the remaining person ends up in a care home, then the council can reclaim all fees for the second spouse from the sale of the property. IMO that's not a bad way to use up your own money - it is on your own living care needs after all.
If the house is owned as tenants in common, then 50% of the house value is considered to belong solely to the person in care, and while the council won't kick you out, when the house is sold (often on the death of the first or second spouse) the council will claim back the fees from the 50% of the value of the house that belonged to the person in care. If the surviving spouse wants to downsize, they might only have half the value of the property to spend on a new place , depending on how much is left after the council reclaims their fees.
When the first TIC dies, and hasn't been in care home, then their half of the house value is held in trust by the beneficiaries of the will, with the remaining spouse holding a lifetime beneficial interest to continue living in it.
Bear in mind that if either of you ends up in a care home, if you limit your care to only what the council will pay for, you will not be in as nice a home as one that you might be able to afford out of your own wealth.