If the parallel cells are exactly the same chemistry - - and they were fully charged to the same voltage independently.
Under discharge, they will remain balanced unless and until they are discharged to an unsafe level. When reasonable discharge rates exist, the cells will stay in balance. A defective cell may discharge
the good cells. You can even charge them in parallel, as long as you used a safe charging current. Usually the limit is whatever 1C rate that applies to the lowest capacity cell.
The safe max current capability will reduce as lower capacity cells energy storage is exhausted.
there are some caveats, in that dissimilar cells will usually have differing internal resistance, which makes a difference in current capability.
At high discharge rates, lead length differences may have an effect.
In an ideal environment for protecting the cells, current limiting devices should be used between each cell. Automotive fuses may be a low cost possibility. Unfortunately this is often not practical in higher current usage, unless a complex and pricy power control scheme is used. (Yes you can buy such things)