I got LG RO for Rs 29000 but the stingy LG did not give the spanner and it was very difficult to unscrew pre filter case . You have to remove the water inlet pipe and empty it and then try , No suitable spanner for unscrewing LG case is available even on line . So I changed the pre filter case available with a spanner
Choosing branded RO is good sir. But on the other side Market available filter won't be suitable for some RO. We have to depend on them for service and cost will be high compared to Multibrand RO.
If the flow going high from the beginning means it's based on water quality and membrane quality used.. if it is in between then change membrane and FR.