Tax advantages / difference between URSSAF and Impots?

I am submitting some unions de recouvrement des cotisations de sécurité sociale et d’allocations familiales (URSAFF) declarations for my business here in France very late. I will be asking URSSAF to allow me to pay at an affordable rate, as I owe quite a lot and have some fines for late submission. I intend to pay a couple of the appropriate taxes levied on my Declarations de Recettes to show them I am willing to pay what I owe.

1. I did not have any cheques to send them, but I have ordered some. It can take two weeks. Can my friend write a cheque on my behalf (if I give him the money) or is this too confusing for URSSAF?
2. Just a very general question as I calculate what I owe. With profession liberale status - URSSAF wants to take 25.5 % and 0.2 % of my earnings from each trimester declaration. This is my only income, my own business proceeds. In the example below:

Person A: First trimester 2015 income of 1,850 euros. Pro rata annual income of 7,400 euros. Taxed at 25.7% in total.
Person B:  First trimester 2015 income of 5,000 euros. Pro rata annual income of 20,000 euros. Taxed as above.

I conclude that both business people are taxed the same, on vastly different personal incomes. But the advantage of being in URSSAF is that they both have a registered and official business, it’s legal to operate in France and both are paying into the system properly.

But my question is this: It seems that the French state recognises low earnings as a problem - as IMPOT does not tax income blow 9,000 euros, but URSSAF don’t also make a distinction for low earners with their own business. So, is there any consideration of this difference of income between person A and person B? Does URSSAF look at the end of the year and give the business person A some tax back?