My mom is fragile physically, but very competent mentally. She lives at home, manages her own medications and takes care of all her bills. However, with her declining health, my sister and I want to make sure she is protected from anything that could happen to change her ability to take care of herself. She would like to designate us as her joint Durable Power of Attorneys. If we take this step, will she still be allowed to write her own checks? We all want to ensure her independence for as long as possible.
Financial is you carry out Moms wishes. You handle her money when she can't. Same with Medical, you're carrying out Moms wishes.
There is "immediate" which starts as soon as its signed and witnessed. "Springing" only becomes in effect when its found the person is incompetent to handle their affairs.
I might also suggest setting up auto-pay for the bulk of her bills. I did this for my mom when she was still in a mild stage of dementia, and she loved it. She could still log into her bank account or look at her paper statement and see the bills being paid. She still felt independent while not having to remember to physically sign checks each month.