I currently race mostly Olympic and sprints on local courses that are rolling to hilly and trying to decide if it makes sense to upgrade race wheels. I currently race on a pair of older Zipp 404s with the aluminum track brake surface (I am guessing they are both circa 2010-2011 - got rear here on ST, bought front locally). My questions:

What, if any, is the likely ultimate performance difference over a 40k bike for wheels with a carbon brake surface vs aluminum track? Assume a current bike split in the 1:05-1:07 range depending on the course. I race pretty often once the season starts and am really not interested in the hassle of also changing brake pads every time I put on race wheels unless there is a clear performance advantage. Relatedly, do any companies even make race wheels with an aluminum track anymore?

What, if any, is the ultimate performance difference between my old Zipp 404s and a new/newer wheel in the same class over the same 40K bike? I cannot afford to drop 2k for new wheels (also looking to get a new bike) so a new pair of 404s is out. Brands I am thinking of are Flo 30/60s, Hed 3s, Boyd or maybe a newer used set of Zipps assuming there would be a noticeable performance advantage. If I get something I would like it to be light, durable and affordable (I know, pick 2).

Thanks in advance.