I don't know anything about that tracer controller but to me it looks like a rebranded Asian controller I've seen on E Bay. For similar money you could get a Morningstar PWM controller and know that you'll have some reliability. PWM will limit you to 12V nominal modules but if you have space, that may be a good solution. There is no really hard and fast rule about 12v or 24V modules being better or worse, it is more about space, budget, and use. Mono or poly modules in the quantity used on an RV is fairly irrelevant, a lot of us have found that the poly panels harvest a good amount of power, especially in low-light environs.
Good luck with your solar, it is a treat to use for RV's.