is RB493 works well as load balancing of 8 dsl lines of 4 MB ? (8DSLX4MB)
in my case Load Balancer(rb-493) ---->86X MT-PPPOE

any suggestion ?

PCC works the same on all RouterOS devices, there are also important attributes like what traffic you want to ass through.

i mean to RB493 processor is enough for this

I would go for the 493AH or 493G models for this. I believe that's 32 mbit total which should be doable, but can't speak from experience.

I've done 3 x PCC on an RB 1300. Barely gets taxed...