I can recommend this one - https://www.amazon.com/Odoland-Resistance-Mobility-Powerlifting-Exercise/dp/B01LED8ZVC/
Comes with a 5th band too.
Also comes with handles, but I don't use those.
Had them almost 2yrs without issue other than the black band fading from black to dirty yellow.
Yes. Resistance training of some kind is important for retaining muscle.
This is the set I bought. https://smile.amazon.com/Odoland-Resistance-Mobility-Powerlifting-Exercise/dp/B01LED8ZVC/r
I just ordered these on Amazon. Haven’t received them yet but they have good reviews.
https://www.amazon.com/dp/B01LED8ZVC/ref=cm_sw_r_cp_awdb_t1_uX3kEbCR6RZG0
Also ordered this bar to go with the bands for deadlifts. It takes a capacity of 800lbs of resistance.
https://www.amazon.com/dp/B07WHWD12D/ref=cm_sw_r_cp_awdb_t1_513kEb176CXNT