If the controller will be near the batteries at all, then #8 from it to the batts is fine for 25 amps. Pigtail to your #6 to the roof. #6 can be very long and not worry about loss at 25 amps. Wiring from individual panels collected to the #6 on the roof can be #10 or 12 (6.2 Isc).
You don't need MPPT and the 40a Grape is half or less of the Tracer cost. 12v panel cost is then the "issue" as usual.
If you went PWM that would mean you care about total panel amps (same as Isc value) and not much about voltage drop or panel heating loss of watts. So you would even be ok with #8 all the way.
If you had the Tri 2030 you could get its matching 30a controller, but if you have a 2025, the Grape is the one to get. Even a simple Solar30 would do the job you are looking at.