Is charge batteries in series faster than in parallel?
Be very careful with powerful chargers to charge your li ion.
One cell can handle 1A load current the other 20A
Don't mix load current with the famous C, if a cell is 3000mah @ 1C your max charge is 3A.
If it is 0.5C it would be max 1.5A charge

Look up the cell specs and adjust your charger to there max.
If a cell is rated with 5A charge or rated with 30A charge.
If you have 10 cells parallel, the max charge would be 4.0 V at 50A or 300A, that depends on your cell structure
If you have 10 cells in series(all the same type btw), your max charging would be 20.0 V at 5A or 20.0 V at 50A.