do what works the best for you. best to avoid knots besides the timber hitch, but if they work..use em!
Native American bowstrings i've seen are all knotted.
My ancestors seem to have been able to survive for thousands of years without a flemish loop...or i wouldn't be here!
the nice thing about a natural fiber string is when it breaks, even out in the field, it can be added to and repaired easily.
I doubt you can do that with B-50...
cord twisted tight makes a "tougher" string - compacted ...but it also has more problems with stretch in the beginning.
but dogbane cordage won't stretch too much and its "waterproof"...it was also used for fishing nets.