That is correct.
All seats must use seat back braces. However seat that are FIA certed and current in the cert (ie less than 5 years) may be run without a seat back brace.
So the rule says everyone needs a brace except for certain ones.
I don't know if the seat you mention is tube frame or not, but I do not suggest a tube frame set. Get fully composite shell or aluminum.
Which seat you get depends on what you like.
Also if the seat has wings for head support you are not required to run a side net. If you do not have side wings for the head you need a right side net too.